CHROMOSOMAL

CHROMOSOMAL
MUTATION
MUTAT ION
• Alteration or error which causes change in the structure or number of chromosomes.
• May either be hereditary, or environment induced.
• Mutation involves a long segment of DNA.
• These mutations can involve deletions, insertions, inversions, or translocations of sections
or segments of DNA.
• In some cases, deleted portions may attach to other chromosomes, disrupting both the
chromosomes losing the DNA and the one gaining it.
• Happens because of a change in chromosome structures, chromosomal rearrangement, or
other chromosomal abnormalities such as a change in chromosome number or missing
chromosome.
• Often takes place during crossing over or cell division.
• Sometimes, chromosomal parts are too slow during the anaphase of mitosis, and this causes
them to go off-track when the cell and nuclei are being rearranged.
• When this transpires, the chromosomes may get digested by nucleases.
• On the other hand, some chromosome sets or segments might get duplicated by accident,
creating a different type of mutation during cell division.
• During crossover, more types of genetic mutations occur as the chromosomes may break
or separate abnormally causing cases of chromosomal disorders.
• These usually happen throughout meiosis and can be artificially or naturally occurring.
• If the type of chromosomal mutation is present on a hereditary gene, then this mutation
will be passed down from generation to generation.
• There may also be chromosomal mutations that are caused by radiation and chemical
molecules.
Chromosomes
• Threadlike structures where DNA is packed.
Karyotype
• Number and appearance of chromosomes (length, banding pattern, centromere position).
• An individual's complete set of chromosomes.
Karyogram
• Photogram of chromosomes.
Autosomes
• Chromosomes 1 - 22
Sex Chromosomes / Allosomes
• Chromosome 23
• XX - female; XY - male
Mechanism of Chromosomal Mutation
• The way the chromosomal mutations work is all based on the type of mutation that occurs.
• Lagging or abnormal pairing of chromosomes can cause a difference in the number of
chromosomes in a cell.
• These chromosomes are not separated during anaphase and cause the additional or
misplacement of chromosomes.
• Conversely, alternations in the chromosomal structure transpire when segments of
chromosomes are digested and also occur when mistakes or accidents are made when the
nucleus is being reorganized.
Types of Chromosomal Mutations
• Most chromosomal mutations are either Chromosomal Mutations I or Chromosomal
mutations II.
• Chromosomal Mutations I involve the processes of inversion, deletion,
duplication/amplification, or translocation.
• Chromosomal Mutations II involves aneuploidy and polyploidy.
1. Chromosomal mutations I
• As mentioned above, the four types of
Chromosomal Mutations I are inversion,
deletion, duplication/amplification, and
translocation.
• These mutations alter the structure of the
chromosome since they tend to break,
and these pieces often form sticky ends.
A. Inversion
• Inversion chromosomal mutation follows the
rules of inversion biology.
• Just as the name implies, the chromosome is
inversed, and its segments are reversed from end
to end.
• A piece of the chromosome is removed then
reattached but in the opposite direction than it was
originally.
• When this does not include the center or the centromere of the chromosome, it is called
paracentric inversion.
• When the inversion does include the centromere, it is pericentric.
• Examples of inversion:
• Two well-known examples of inversion chromosomal mutations are the inversion
of chromosome 12 creating the tallest teenager in the world.
• This inversion mutation is also seen in a species of Coelopa frigida insect.
• This mutation gives the insect a variety of physical attributes that usually occur in
the smaller version of the organism rather than the larger.
B. Deletion
• Also known as partial monosomies, these occur when a
piece of a chromosome accidentally gets removed or
deleted.
• There can be cases with one piece deleted at the end
(terminal deletion), two deletions – one deleted within the
chromosome, and one on the end – (interstitial deletion).
• Microdeletions also occur when the deletions in the
chromosomes are too small to be detected.
• Examples of Deletion:
• Cri-du-chat syndrome (condition as a result of a
deletion of a piece of chromosome 5) and 22q11.2 deletion syndrome are examples
of deletions that occur in the chromosomes.
• Cri-du-chat symptoms are named this way since infants who suffer from this
condition often have a high-pitch cry similar to that of a cat.
• The microdeletion of chromosome 22 causes 22q11.2 deletion syndrome that often
results in a variety of syndromes including heart problems, infections, and
interesting facial features.
C. Duplication/Amplifications
• As the name implies, an extra copy of a segment or the
entire chromosome is present in the nucleus. These are
also known as partial trisomies.
• Often an organism that usually has two copies of a
chromosome will have three in the case of duplication.
• This can happen anywhere along the chromosome
whether in the middle or on the ends.
• Examples of Duplication/Amplifications:
• When an extra copy of chromosome 22 is
made, it results in 22q11.2 duplication
syndrome. This autosomal dominant condition
can often cause slow vertical growth, weak
muscle tone, and intellectual disabilities.
• MECP2 duplication syndrome can also cause weak muscle tone as well as
intellectual disabilities. This duplication mutation is often seen in males and is
caused by the duplication of the MECP2 gene.

D. Translocation
• Translocation chromosomal mutation follows the route of biological translocation.
• This happens when a segment of a chromosome breaks
off and then relocates to a completely different
chromosome.
• This creates fusion chromosomes as one type of
chromosome fuses with another.
• Reciprocal translocation occurs when pieces of
chromosomes “swap” places.
• Robertsonian translocation occurs when a segment of a
chromosome is attached to another chromosome, causing
an elongation of it.
• These can be balanced or unbalanced, where the chromosome is fully functional with no
missing genetic information (balanced) or with important missing pieces and cannot
function as normal (unbalanced).
• Examples of Translocation:
• The translocation of chromosome 21 onto the 14th chromosome causes the
common genetic mutation of down syndrome.
• This mutation is also the cause of many leukemias and lymphomas. For instance, a
translocation between the 15th and 17th chromosomes causes Acute promyelocytic
leukemia (APL) and translocation between the 12th and 15th or the 1st and 12th
chromosomes cause Acute myelogenous leukemia (AML).

E. Insertion
• A type of chromosomal abnormality in which a
DNA sequence is inserted into a gene, disrupting the
normal structure and function of that gene.
• A portion of a chromosome is added to another
chromosome.

II. Chromosomal Mutations II

• The other type of chromosomal mutation categories Chromosomal mutations II than
consists of aneuploidy and polyploidy.
• The general category of these is called heteroploidy since they cause a mutation by
changing the number of chromosomes present in the cell.
A. Aneuploidy
• This mutation either causes the loss or addition
of a chromosome by the contortion of the
chromosome set.
• Nondisjunction during meiosis or mitosis
usually results in this mutation.
• Monosomy (2n - 1) ; n = 23
• Trisomy (2n + 1) ; n = 23
• Examples of Aneuploidy:
• Down syndrome is also an example of aneuploidy. It is caused by the trisomy is the
nondisjunction of chromosome 21. It usually causes mental retardation that can be
mild or even severe.
B. Polyploidy
• This mutation causes the creation of two sets of genomes within an organism.
• It is not usually common naturally however; it can be observed in some plants.
• It usually causes effects like giantism and the reduction of fertility.
• Examples of Polyploidy:
• The “Doob” plant in South Asia undergoes this type of mutation being triploid and
sterile. It can, however, be cultivated vegetatively.

Through the Polyploidy, it can create vegetables that are seedless and
hassle-free from eating such as watermelon and tomatoes.

ADVANTAGES OF CHROMOSOMAL MUTATION

Chromosomal mutation, which has had a significant impact on survival while also boosting and
diversifying humanity, has enabled humans to adapt to their environment.
1. SURVIVAL
As the environment and society has continuously to raise such rare, long treatment and
fatal diseases, humans have been able to adapt to the surroundings because of mutations
that increase their level of survival. Among other things, mutations have been responsible
for HIV immunity, malaria resistance, and antibiotic resistance in microorganisms and
lactose tolerance which have been successfully done throughout the years. For instance, a
rare gene mutation in Ecuador that causes shortness of height has turned out to be
beneficial. The mutation affects the way the body uses growth hormones. It causes a
condition called Laron syndrome which is proven to be both cancer and diabetes resistance.
2. DIVERSITY
As living things, chromosomal mutations frequently contribute to our individuality.
Chromosome mutations gave rise to physical traits like blue eyes, blonde hair, and even
freckles, allowing humans to develop a wider range of physical characteristics. Variation
within humanity is encouraged by characteristics like hair color, eye color, freckles, and
other traits brought on by these genetic variations.

DISADVANTAGES OF CHROMOSOMAL MUTATION

On the other hand, despite its advantageous outcomes chromosomal mutations can be harmful and
dangerous to the existence of living organisms as it can lead to numerous and more devastating
issues.
1. GENETIC DISORDERS
These are conditions or limitations brought on by DNA mutations in the organism. These
might be minor genetic problems that hardly impact the person or more serious problems
that cause the person serious concerns. Even a little chromosomal alteration might have a
compelling impact on a situation.
2. OTHER DISEASES
Chromosome mutations are the cause of conditions such as diabetes, cancer, and even
asthma. These illnesses can result in major health problems, which in some situations can
be fatal for the person who has these conditions. For example, African Americans are
affected and experiencing a widespread illness of SCD and SCT. This is because SCD and
SCT are genetic characteristics that individuals evolved as a means of defense against
malaria.
7 BEAUTIFUL MUTATIONS
1. Heterochromia
The presence of different colored eyes to the same person or a person with more than one eye
color is common in animals such as cats and dogs but rare in humans. This condition may also
worsen because of an illness, accident, or medicine called acquired heterochromia.
Types of Heterochromia
• Center Heterochromia
The most common type of Heterochromia in which the hue of the border of the pupils is
varied. The iris is a distinct color throughout, with a hint of gold towards the border of the
pupils.
• Complete Heterochromia
People with this condition have eyes that are an entirely different color than the other eye.
For instance, one eye may have blue in color and green on the other one.
• Sectoral or Segmental Heterochromia
Also known as partial heterochromia wherein a part of an iris has a different color from
the remaining part or area. The sectoral heterochromia resembles a splotchy area on the
iris and doesn't cause the pupil to form a ring.

Center Heterochromia Complete Heterochromia Sectoral or Segmental

2. Double Eyelashes
An additional row of eyelashes is referred to as distichiasis or
double eyelashes. Its rareness is estimated to affect one in 10,000
persons worldwide.

3. Red hair
Red hair is caused by the melanocortin 1 receptor (MC1R), a gene that
influences the pigmentation of the skin and hair. A person's increased
production of the red pheomelanin pigment, which is additionally found
in our lips and nipples, led to the red hair mutation. Depending on the
gene carried the pigment might look differently, resulting in strawberry
blonde, brownish auburn, or fiery red hair. Redheads respond to pain
differently than those with other prevalent hair hues. It is estimated that one in 100 people
worldwide have this rarity.
4. Freckles
A combination of factors including the type of melanin that a person's body generates, genetics
also play a significant part in who is more prone to get freckles. Pheomelanin and eumelanin are
two different forms of melanin that the body may manufacture.
Pheomelanin does not shield the skin from UV radiation like
eumelanin does. The MC1R (Melanocortin-1 Receptor) gene
controls the kind of melanin the body makes. More pheomelanin is
produced when the MC1R gene's instructions to make eumelanin
are suppressed and the overproduction of pheomelanin results in
freckles.

5. Blue eyes
On chromosome 15, there are two key genes called OCA2 and
HERC2 that produce blue eyes. People who possess several common
genetic variations in the OCA2 gene will have blue eyes instead of
brown because the changes cause the iris to produce less melanin.

6. Cleft Chin
A chin with a Y-shaped indentation in the center is referred to as having
a cleft chin. Usually, it is a hereditary characteristic.

7. No-show wisdom teeth

Wisdom teeth are lacking because of a random DNA mutation that
happened about 400,000 years ago. This mutation prevented the
development of wisdom teeth in a small number of people, a
characteristic that is common nowadays. Since the earliest fossils
without third molars are in China and are between, it is possible that
the first mutation began there.
APPLICATION OF CHROMOSOMAL MUTATION
• Various genetic and hereditary disorders can be treated using chromosomal alterations, and in
certain cases, they can even be eliminated.
• A crucial role in the evolution of various living species' chromosome and genome changes has
been played by chromosomal mutations.
• Chromosome mutations can be used to address biological problems when they are created and
ordered in certain ways.
• Chromosome Mutation II has been used to produce polyploidy, which results in vegetables and
fruits without seeds.
CANCER CELL
• Even when there are sufficient cells, they continue to grow and generate.
• Variance in cell shape and dimension due to the disorderly cell organization
• They remain immature since their cells lack complete growth and they divide rapidly
before they do.
• Cells cannot be repaired or replaced.
• Take no action when other cells provide signal or communications.
INDUCED MUTATIONS
• After an organism's DNA undergoes exposure to a MUTAGEN which can be either
physical or chemical agents, a form of mutation known as an "induced mutation" develops.
• An alteration in the sex cell genes is an instance of an induced mutation. The sex cell genes
become mutated when the gonads are exposed to mutagens like radiation.
• A variety of external variables, including certain chemicals and radiation, can harm DNA.
• High energy radiation, toxic chemicals, extreme temperatures, and radioactive substances.
Physical mutagens: X-rays, cosmic waves, particle radiation, gamma rays, and UV radiation.
Chemical Mutagens: Examples include Hydroxylamine, Proflavine, Colchicine, Ethyl methyl
sulfate Mustard Gas, Nitrous Oxide, mitomycin, 5-Bromouracil and a wide variety of chemicals.
RADIATION
• Another sort of environmental mutagen that can directly alter a cell's DNA is radiation.
• Damages biological systems at many levels
• A few radiation types are particularly ionized reactive compounds that can induce DNA
mutation.
• It is feasible to repair, however if changes occur, the system is overloaded and/or cell death
then cancer may develop.
SPONTANEOUS MUTATION
• Unidentified factors result in spontaneous mutations, which happen naturally. However, it
might result from a regular cell's actions, including errors made during DNA replication.
• In the event of the absence of mutagens, a spontaneous mutation is a form of mutation that
happens naturally such as mistakes in DNA replication, repair, and recombination are all
causes of these occurrences. X-rays and chemical substances are examples of mutagens—
agents that cause mutation.
Methods of repairing DNA damage sustained throughout the duration of a cell's lifespan and
oversights made during DNA replication.
INDUCED MUTATION SPONTANEOUS MUTATION
UV LIGHT ERROR IN DNA REPAIR
RADIATION ERROR IN TRANSCRIPTION
CHEMICALS ERROR IN POLYMERIZATION
ERROR IN REPLICATION

APOPTOSIS - The mechanism of programmable cell death is called apoptosis or cellular suicide.
It is used in the early stages of cellular growth to remove undesirable cells.
1. Proofreading
- correcting mistakes made throughout DNA replication and searching for the most mismatched
bases in a procedure.
- DNA polymerases are an assortment of enzymes that facilitate DNA synthesis during
replication. It can "check the work" with every component they add while copying.
- Before proceeding with DNA synthesis, the polymerase will immediately delete and repair the
nucleotide if it discovers that a wrong nucleotide has been introduced.
2. Mismatched Repair
- the process of detecting and replacing any mismatched bases that happens after DNA replication.
- those that were overlooked to be repaired or fixed during the proofreading.
 Proofreading Mismatched Repair

APPLIED GENETICS
APPLI ED G E NETICS
• aimed at altering organisms' genomes to maximize their usefulness to humanity.
• the tangible application of genetics to medical, agricultural, and microbiological breeding is
known as applied genetics.
• it is the method of creating a genetic product utilizing gene hypotheses or theories.
• the application of genetics theory to real-world situations.
BREEDING STRATEGIES

• Selective Breeding

- The most traditional way to breed desirable attributes in offspring is to choose parents
who possess those best features and traits.
- The combination of gene variations that are handed down from one generation to the
next affects an organism's traits to some extent.
- specifies a breed to repair or eliminate features, illnesses, or qualities in the offspring.
- For instance, dog owners selectively choose the parents of puppies to inherit and pass
on favorable traits such as German Shepherd, Toy Poodles and Great Danes.

TYPES OF SELECTIVE BREEDING

• Inbreeding
- includes breeding individuals that are closely related to maintain desirable traits.
- The generation of offspring through the mating or breeding of people or other living
things that are genetically closely associated with one another.
- can result in defects, organ failure, physical flaws, and other abnormalities.
- the offspring will be nearly identical in appearance and will eventually produce
identical offspring after several generations of inbreeding. The term "thoroughbred" or
"purebred" is used to characterize an organism when this occurs.
Purebred
- both parents are of the same breed
- contain two recessives or two dominant genes for a certain characteristic.
- Purebred examples are Labrador Retriever dogs and Siamese cats.
Linebreeding
- a type of inbreeding
- consists of the mating of distant relatives, such as cousins.
- this slows down the pace by which the breed becomes "purebred," lowering the danger
of illness that occasionally affects purebred characteristics.
• Outbreeding
- occurs when two unrelated organisms’ mate.
• Outcrossing
- Mating with another member of the same breed who is not a 4–6-year generational
ancestor.
• Interspecific Hybridization
 - Male and female animals of two different related species are mated.
• Cross Breeding or Hybridizing
- entails mating two distinct individuals.
- frequently utilized to create offspring from two separate persons that have desired
traits.
- For instance, Poodles and Labrador Retrievers are bred to produce hybrids that have
both the composed, trainable nature of the Labrador and the low shedding coat of the
Poodle. The resulting "Labradoodle" makes an allergy-friendly dog.
- Disease resistant, produce more offspring, grow faster.
- will produce less predictable and inconsistent outcomes.

BREEDING STRATEGIES SAME BREED SAME ANCESTORS

INBREEDING ✓ ✓
OUTCROSSING ✓ X
CROSS BREEDING X X

MULE
- a hybrid from a combination of a male donkey and a female horse.
- Mules are tough-working animals in some of the hardest situations because they
consume less food and have more endurance than horses of the same dimensions and
weight.

Luther Burbank
• American plant breeder
• Luther Burbank (1849-1926) was sometimes called
the 'Plant Magician' for his experimental work with
plants.
• American plant breeder whose prodigious
production of useful varieties of fruits, flowers,
vegetables, and grasses encouraged the
development of plant breeding into a modern
science.
• Reared on a farm, Burbank received little more than
a high school education, but he was profoundly
influenced by the books of Charles Darwin,
especially The Variation of Animals and Plants
Under Domestication (1868).
• He wrote Luther Burbank: His Methods and
Discoveries and Their Practical Application, 12 vol.
(1914–15); How Plants Are Trained to Work for Man, 8 vol. (1921); and a series of
descriptive catalogs, New Creations in Fruits and Flowers (1893–1901). With Wilbur Hall
he wrote an autobiography, Harvest of the Years (1927).

Luther Burbank's contributions in applied genetics

1. Development of New Plant Varieties:
• Burbank introduced numerous new plant varieties through his breeding experiments,
including fruits, vegetables, and flowers.
• He created over 800 new varieties of plants, including the Santa Rosa plum, Shasta daisy,
and the Russet Burbank potato.
• including 113 varieties of plums, 20 of which are still commercially important,
especially in California and South Africa.
• 10 commercial varieties of berries.
• and more than 50 varieties of lilies.
• Russet Burbank Potato– The characteristics, low moisture, and high starch content
– are one of the most popular potato varieties in the United States.
 – They were bred by the US plant breeder Luther Burbank (Massachusetts) in 1902
in a bid to improve the disease resistance of Irish potato varieties being used at that
time.
– Their long oblong shape makes them great for French fries (they're the potato
used in McDonald's fries).

Russet Burbank Potato Shasta Daisy Santo Rosa plum

2. Hybridization Techniques:
- Burbank extensively used hybridization to create new plant varieties with desirable traits.
- He experimented with crossbreeding different plant species to produce hybrids that
combined the best characteristics of both parents.
3. Selective Breeding:
- Burbank practiced selective breeding to enhance specific traits in plants.
- He carefully chose parent plants with desirable characteristics, such as disease resistance,
fruit size, or flavor, and crossed them to produce offspring with those desired traits.
4. Improvement of Agricultural Crops:
- Burbank focused on improving agricultural crops by developing varieties that were more
productive, disease-resistant, and better suited to various climates.
- His work with the Russet Burbank potato, a highly successful variety, revolutionized potato
farming and became widely adopted in the industry.
AN INTRODUCTION TO PLANT BREEDING
• What is Plant Breeding?
o Plant breeding is a very old technique that has been practiced for many years, ensuring
food security and helping farmers grow and produce resilient, stronger, and faster-growing crops
in a wider variety of temperatures and climates.
o It is the science of applying genetic principles, changing, and/or intentionally manipulating
the genetic traits of plant species in order to produce offspring with the desired varieties or plant
types.
o These new plant varieties are expected to adapt to human needs more efficiently, improving
the quality of nutrition in products for humans and animals.
o It is also suited for cultivation because it gives better yields and has good resistance to
diseases.
• Plant Breeding as a systematic process
o Plant breeding is a systematic process. The entire process of plant breeding, from choosing
desirable qualities of plants to the final product, is broadly divided into five (5) main steps.
Step 1: Collection of Variability
Step 2: Evaluation and Selection of Parents
Step 3: Cross Hybridization Among the Selected Parents
The term heterosis or hybrid vigor was coined by Shull in 1912. However, heterosis was
first studied by Joseph Kolreuter in 1763, followed by Charles Darwin in 1876.
 Shull Joseph Kolreuter Charles Darwin
Artificial hybridization is the production of hybrids by cross pollinating two separate plants
under controlled conditions under the supervision of the plant breeder. This process of artificial
hybridization in plants involves various steps. These are as follows:
- Selection of parents with desired characters – care is taken while selecting parents for the
hybridization program. All the desired characters should be present in the parents, which are
required in the new crop variety.
- Emasculation – anthers or male parts of the flowers are removed. Now, a flower contains
only female parts. This is done to prevent self-pollination among flowers.
- Bagging and tagging – soon after emasculation, the carpets are covered with polythene
bags to prevent contamination or stigma from foreign pollen.
- Collection of pollen grains – at maturity, the pollen grains are collected from the desired
parent plant in dry plastic bags.
- Artificial Pollination – when the stigma of the emasculated flower matures, the polythene
bag is removed, and with the help of a brush, fresh pollen from selected plants is dusted over the
receptive stigma of the female.
- Tagging – a tag is a piece of relevant information attached to the plant. The tag bears
information like the date of emasculation, the date of crossing, the details of male and female
parents, etc.
- Desirable combination of variations – seeds obtained after crossing are sown and evaluated
for desirable and undesirable traits and are screened properly.
- Back crossing – if desired traits are absent in the progeny, then they are backcrossed again
until the desired traits are obtained.
Step 4: Selection and Testing of Superior Recombinants
Step 5: Multiplication of Improved Seed
II. PLANT BREEDING METHODS
a. Reproduction in Crop Plants and its Relation to Plant Breeding Methods
• Modes of Reproduction
Modes of plant reproduction determine the genetic constitution of crop plants. The modes
of reproduction in crop plants are broadly grouped into two categories: asexual and sexual.
o Asexual Reproduction
Asexual reproduction does not involve the fusion of male and female gametes. New plants
may develop from vegetative parts of the plant (vegetative reproduction) or may arise from
embryos that develop without fertilization (apomixis). Vegetative reproduction may occur through
modified underground and sub-aerial stems and through bulbils.
- underground stems include the tuber, bulb, rhizome, and corm
- subaerial stems include runners, stolons, suckers, etc
- bulbils are modified flowers that develop directly into plants without the formation of
seeds, like garlic.
- stem cuttings are commercially used in the propagation of sugar cane, grapes, roses, sweet
potatoes, etc.
- Similarly, layering, budding, and grafting are common practices in the propagation of fruit
trees.
The significance of vegetative reproduction is that a desirable plant can be used directly as
a variety, regardless of whether it is homozygous or heterozygous.
• Apomixis
In apomixis, seeds are formed and embryos develop without fertilization. Three major
groups of apomixis are known: adventive embryony (polyembryony), apospory, and diplospory.
- In adventive embryony, embryos develop directly from vegetative cells of the ovule, such
as the nucellus, integument, and chalaza.
- In apospory, some vegetative cells of the ovule develop into unreduced embryo sacs
without meiosis. The embryo may develop from the egg cell or some other cell in the embryo sac.
- In diplospory, an embryo sac is produced from the megaspore, which may be haploid or
diploid. Diplospory leads to parthenogenesis, or apagamy. In the former, the embryo develops the
egg cell, while in the latter, synergids or antipodal cells develop into an embryo.
Apomixis are useful when the breeder wants to maintain varieties, but not when inbreeds
or hybrids are desired.
o Sexual Reproduction
Sexual reproduction involves the fusion of male and female gametes to form a zygote,
which develops into an embryo in specialized structures called flowers.
- A flower containing both stamens and a pistil is a perfect or hermaphrodite flower.
- If it contains stamens but not pistil, it is known as a staminate flower.
- A pistillate flower contains pistil but not stamens.

• Anthesis and Modes of Pollination

In the process of flowering, the first opening of the flower is known as anthesis. Its details
vary from plant to plant and are greatly affected by environmental factors like humidity and
temperature.
Pollination refers to the transfer of pollen grains from anthers to stigmas. When pollen
from another plant falls on the stigma of the same plant, self-pollination (autogamy) occurs, but
when it is transmitted to the stigma of a different plant, cross-pollination (allogamy) takes place.
o Self-pollination (Inbreeding)
Plants that are fertilized by themselves. There are various mechanisms that promote self-
pollination:
- Cleistogamy: The flower does not open, and this ensures complete self-pollination
since foreign pollen cannot reach the stigma of the closed flower.
- Chasmogamy: The flowers open but only after pollination takes place.
o Cross-pollination (Outbreeding)
Cross-pollination is defined as the deposition of pollen grains from one flower on the
stigma of another flower. Commonly, the process is done by insects and wind. The mechanisms
that promote cross-pollination are:
i. Unisexuality (dicliny): either staminate or pistillate flower; it is of two types.
a. Monoecy: staminate or pistillate flowers occur in the same plant.
b. Dioecy: staminate and pistillate flowers are present on different plants.
ii. Dichogamy: stamens and pistils of hermaphrodite flowers mature at different times.
a. Protogyny: pistils mature before stamens.
b. Protandry: stamens mature before pistils.
iii. Stigma is covered with waxy film that is often broken by bees.
iv. Self-incompatibility: pollen fails to pollinate or fertilize an egg on the same plant. It is
generally divided into two groups:
a. Heteromorphic systems (different morphologies)
b. Homomorphic systems (same structures but controlled by genetics)
v. Male sterility: the absence of functional or non-functional pollen grains in hermaphrodite
flowers. It is classified into three groups:
a. Genetic: is used in hybrid seed production.
b. Cytoplasmic: is determined by the cytoplasm; may be transferred and maintained
in a given variety by using that variety as a pollinator in six to seven successive generations
of a backcrossing program.
c. Cytoplasmic-genetic: is a case of cytoplasmic male sterility where a nuclear gene
for restoring the fertility in the male sterile line is known; is used to produce hybrid seeds
in maize and sorghum.
o Partially allogamous or often cross-pollinated crops
These are crops that have cross-pollination that often exceeds 5% and may reach 50%.
 • Relevance of Modes of Reproduction
Modes of reproduction and pollination are important in plant breeding since they determine
the genetic constitution of the species, simplify pollination control, and are useful in maintaining
the stability of varieties after release.
b. Methods of Breeding in Self Pollinated Crops
• Mass Selection
In mass selection, a large number of plants of similar phenotype are selected and their seeds
are mixed together to establish a new variety.
• Pure Line Selection
Individual plant selection is another name for pure line selection. With this technique, a lot
of plants are picked out and plucked one by one. The best progeny is then issued as a pure line
variety, followed by the release of each of their individual offspring.
• Pedigree Selection
In the pedigree method, selection is used from segregating generations, where individual
plants are selected from F2 and subsequent generations.
• Bulk Method
The population method or mass method of breeding are other names for the bulk method.
With this approach, the F2 and succeeding generations are harvested in large quantities to produce
the following generation. Individual plants are harvested and assessed at the conclusion of the
bulking period similarly to the pedigree technique of breeding. Bulking may last anywhere from
6-7 and 30 generations or more.
• Single Seed Method
Single seed descent method is a selection method carried out by selecting only one seed
from each plant.
• Back Cross Method
The objective of the backcross method is to improve one or two defects of an adapted high
yielding variety, the characters lacking in the variety are transferred to it without changing its
genotype, except the gene being transferred.
c. Methods of Breeding in Cross Pollinated Crops
Crops that have been cross-pollinated exhibit varying inbreeding depression, ranging from
mild to severe, and are extremely heterozygous as well as diverse. Therefore, cross-pollinated crop
breeding techniques try to prevent or reduce inbreeding.
• Population Improvement
There are two major types of population improvement methods: without progeny testing
(the progenies of selected plants based on their phenotype are not tested like those of mass
selection) and with progeny testing (plants are initially selected based on phenotype, but the final
selection of plants for the next generation is based on progeny testing).
• Hybrid Breeding
The hybrid varieties are the first generation (F1) from crosses between pure lines, inbreds,
clones, or other population that are genetically dissimilar while inbred lines are nearly homozygous
line obtained by continuous inbreeding of a cross pollinated species with selection accompanying
inbreeding and is maintained by close inbreeding (self-pollination).
d. Other Plant Breeding Methods
• Hybridizing or crossbreeding
In this hybrid breeding process, the two different
selected breeds are crossed over to produce offspring that
are more efficient and productive than the parent plants;
Parents with different traits are crossed and can also be
performed in plants.
• Embryo culture technique
- An in vitro development, or maintenance of isolated mature or
immature embryos on a nutrient medium.
- The technique makes use of inexpensive components of the
standard media and minimum transfer of culture.
- Aims to cut down on production cost while increasing plant
production.

• Synthetic seed engineering

- Man-made seeds, the products of genetic engineering.
- Produced from stem cells grown and cultured in the laboratory.
- These plants may also be pathogen-free, which means that they
are suitable for export and transport across international
borders.

• Gene slicing technique

- Process of taking genes from one organism and combining
them into the genes of another.
- A gene or genetic trait can be inserted into a plant to obtain
a result.
- Recombinant DNA is produced by slicing.

• Molecular Marker-Assisted Selection

- This method uses classical inbreeding or
backcrossing and hybridization techniques, with a very
important difference.
o Instead of choosing desirable plants based on the way
they appear or grow, breeders select plants after
confirming the information on the genes the plants
inherited from their parents. This is somewhat guessing
and hence, the researchers should confirm the gene that
is present, not just assume it is before they move forward with breeding the plant.
• Mutation Breeding
- Naturally occurring genetic mutations are
seen in many organisms like plants, animals,
etc. If these types of random examples are
found and seen as an improvement, then, they
can be used to create new plant varieties.
- Alternatively, mutations can be artificially
encouraged or induced in plants by exposure
to radiation or chemicals.
 • Polyploidy Breeding
- Most of the plants are diploid in nature. Plants with three or
more complete sets of chromosomes are usually common and are
referred to or known as polyploids.
- The increase of chromosome sets per cell can be artificially
induced by using the chemical colchicine, which leads to a doubling
of the chromosome number.
- Generally, the main effect of polyploidy is an increase in size
and genetic variability.
- Polyploid plants often have lower fertility and grow more
slowly.

• Gene Editing
- Gene editing or genome editing allows breeding objectives to be
achieved more quickly and precisely than ever before, thereby expanding
the genetic variation of a wider variety of crops.
- This ensures high yield, develops resistance in plants against pests,
high-quality seeds, and other agricultural products, etc. Usually, it targets
very specific plant characteristics with razor-like precision.

• Somatic Hybridization
- The fused protoplast is grown in vitro with the aim to
obtain a hybrid plant. So the in vitro fusion of plant
protoplasts derived either from somatic cells of the
same plant or from two genetically different plants is
called somatic hybridization.
- Sometimes the protoplasts from vegetative cells and
gametic cells are fused and such fusion is called
somato-gametic hybridization.

IV. OBJECTIVES AND STRATEGIES OF PLANT BREEDING

For effective use of resources, plant breeding programs must establish precise breeding
goals depending on plant species and the growing environment. Breeders must know what they
hope to produce in the end, including pure lines, hybrids, synthetics, composites, and clones.
Breeders typically work to enhance a plant's traits to make it more desirable from an economic and
agronomic standpoint. The following is a list of the most typical breeding goals:
• Improving Yield
• Improving Quality
• Improving Disease or Pest Resistance
• Environmental Stress Tolerance
• Improved Adaptation
• Suitability to Mechanization

GENETIC IMPROVEMENTS ON HUMANS

• The Mendelian laws applies to humans.
 • Researchers theorized that men may be able to discover the secret of life, the cure of
hereditary diseases and defects and possibly produce a race with superior qualities through
genetic engineering.
• Moral and ethical issues are involved in manipulating genes to clone human beings.
Mendelian Inheritance in Humans
• Characteristics that are encoded in DNA are called genetic traits.
• Different types of human traits are inherited in different ways.
• Some human traits have simple inheritance patterns like the traits that Gregor Mendel
studied in pea plants.
• Other human traits have more complex inheritance patterns.
• Mendelian inheritance refers to the inheritance of traits controlled by a single gene with
two alleles, one of which may be dominant to the other.
• Not many human traits are controlled by a single gene with two alleles, but they are a good
starting point for understanding human heredity.
• How Mendelian traits are inherited depends on whether the traits are controlled by genes
on autosomes or the X chromosome.
Designer Baby / GM Baby
• In its simplest definition, a designer baby is an
embryo that has been genetically modified (or
gene-edited) for the sake of producing a child
with specific traits.
• In some cases, unfavorable characteristics or
bad traits (like genetic disease) may be removed,
or favorable traits (like enhanced intelligence or
strength) might be added.
• Scientists saw the potential to not just optimize
genes for disease prevention, but also to choose
aesthetics and personality traits.
• There are various technologies involved in the creation of a GM baby.
• One protocol is Preimplantation Genetic Diagnosis (PGD), where embryotic genetic
defects are identified preimplantation and only embryos devoid of certain genetic disorders
are implanted.
• Most recently in the news is CRISPR genetic engineering, which was originally created in
the 1980’s.
• An evolution of the genetic technology is known as CRISPR-CAS9.
• CRISPR designer babies are created by modifying DNA fragments to prevent and correct
disease-causing genetic errors.
• CAS9 is a special technology which can remove or add certain types of genes from a DNA
molecule, and most recently has been used after fertilization for gene-edited embryos.
• Gen 1 – Traditional IVF (in vitro fertilization)
• Gen 2 – Intracytoplasmic Sperm Injection (ICSI)
• Gen 3 – Preimplantation Genetic Screening/Diagnosis (PGS/PGD)
• Gen 4 – Nuclear Transfer (HER IVF/3-Parent Baby Technology)
• Gen 5 – Gene Editing (GMO babies/Designer Babies)
• Gen 6 – Artificial Gametes (Stem Cells)
Nicholas Agar, Professor of Ethics in Victoria University
• “We are no longer living in a time when we can say we either want to enhance or we don’t."
**Chinese researchers announced they had attempted to genetically alter 213 embryos to make
them HIV resistant. Only four of the embryos were successfully changed and all were ultimately
destroyed.
June 21, 2016
 • The U.S. government announced that it had approved the first human trials using CRISPR,
in this case to strengthen the cancer-fighting properties of the immune systems of patients
suffering from melanoma and other deadly cancers.
Jennifer Doudna, co-inventor of CRISPR and others
• CRISPR could provide new treatments or even cures to some of today’s most feared
diseases – not only cancer, but Alzheimer’s disease, Parkinson’s disease and others.
Germline Editing
• Making genetic changes at the embryonic stage.
• The logic is simple: alter the gene lines in an embryo’s eight or 16 cell stage (to, say,
eliminate the gene for Tay-Sachs disease) and that change will occur in each of the resulting
person’s trillions of cells – not to mention in the cells of their descendants.
Recombinant DNA
• general name for a piece of DNA that has been created by the combination of at least two
strands
• sometimes called chimeric DNA, because they can be made of material from two
different species, like the mythical chimera.

Genomes are lengthy!

The human genome has 3 x 10^9 bp which is equal to 3000 km (1800 miles) if 1 bp = 1 mm.
This length alone equates to the depth of the Midnight Zone (Bathypelagic Zone) beneath the
ocean's surface, which is so deep that it receives no sunlight at all.
E.coli, despite being miniscule, has a genome length of 4 x 10^6 bp or 4 km (2.5 miles).
Imagine, an organism that is unseen by the naked eye contains a genome that is great in length!
IN FOCUS: Recombinant DNA Technology
• Genetic engineering or recombinant DNA technology refers to various techniques and
procedures used in gene manipulation.
• Recombinant DNA technology involves modifying and recombining DNAs to produce
desired products such as proteins, or animals and plants with desirable traits.
• It has wide-ranging applications in the fields of medicine, forensic, pharmaceuticals and
agriculture, especially in improving livestock and crop production.
Tools Used in Recombinant DNA Technology
1. Target DNA, that is, the gene of interest
2. Restriction enzymes act as scissors that are used to cut DNA into fragments
3. DNA cloning vectors to carry the target gene into a host cell
4. Host cell, that is, bacterial cell that allows the cloning vector to replicate within it
5. Modifying enzymes that join the DNA fragments to form rDNA
• Restriction enzymes
• are naturally found in certain bacteria that are resistant to bacteriophage infections. These
enzymes function as defense mechanisms protecting the bacteria.
• A particular restriction enzyme identifies a specific base sequence known as restriction
site and cuts the DNA at a specific point between two nucleotides in the site.
• The restriction site (sequence) is a sequence that consists of the same four to eight
nucleotides on both DNA strands but arranged in opposite directions. The sequence is
said to be palindromic.

*Palindrome in Genetics
• A DNA or RNA that reads the same in both directions.
 • Different restriction enzymes cleave at different base sequences. For example, the
restriction enzyme EcoRI recognizes the sequence GAATTC

Table 1. Restriction enzymes, their sources, and restriction sequences

(Note: arrows (↓ and ↑) denote cleavage point)

Enzyme Source What sequence does it Restriction

recognize? sequence

EcoRI E. coli RY 13 GAATTC G↓AATTC

CTTAA↑G

BamHI Bacillus GGATCC G↓GATCC

amyloliquefaciens CCTAGG

TaqI Thermus aquaticus TCGA T↓CGA

AGC↑T

SmaI Serratia marcescens CCCGGG CCC↓GGG

GGG↑CCC

PovII Proteus vulgaris CAGCTG CAG↓CTG

GTC↑GAC

HaeIII Haemophilus egyptius GGCC GG↓CC

CC↑GG
Cleavage Point - where the DNA is cut by the restriction enzymes
• EcoRI (restriction sequence: G↓AATTC) cuts the DNA strand between G and A;
CTTAA↑G
thus, the DNA fragments result with sticky ends.

• SmaI (restriction sequence: CCC↓GGG) cuts DNA strands between C and G,

GGG↑CCC
Which produces DNA fragments with blunt ends.
 • DNA cloning vectors
• Cloning vectors are molecules that are able to carry foreign DNAs into a host cell. The
foreign DNA is inserted into a cloning vector which then replicates in the host cell.

Characteristics of cloning vectors:

(a) Vectors are able to accept foreign DNA in multiple cloning sites (MCS), that is, the vectors
possess many restriction sites for many restriction enzymes.

(b) Vectors are able to replicate freely and rapidly thus producing multiple copies of the
foreign DNA they carry.

(c) Vectors contain genes which can be useful to bacteria such as amp which codes for
antibiotic resistance.

Examples of Cloning Vectors:

Plasmids
• Plasmids are small, circular DNA molecules which occur naturally in addition to the
bacterial chromosome.
• They are derived from a plasmid and are able to replicate independently from the
bacterial chromosome in a bacterial cell.
• The plasmid that carries a foreign gene is known as a recombinant plasmid and is inserted
into the host cell through transformation.
Bacteriophages
• Bacteriophages are bacteria-infecting viruses, that is, they infect and replicate only in
bacterial cells.
• The bacteriophage DNA is a linear double helix molecule.
• The commonly used bacteriophage is λ2001 (lambda 2001).
Cosmids
• are a combination of bacteriophages and plasmids.
• Cos + Plasmid = Cosmid. The ‘cos’ is derived from the Lambda phage cos sequence,
which is found in bacteriophages.
• Host cell
• A host cell is a cell which is able to accept foreign DNA, that is, the cloning vectors and
allow the vectors to multiply. A host cell can be a prokaryotic cell such as the bacteria,
E. coli or a eukaryotic cell such as yeast or animal cell.

Characteristics of a host cell (for example, E. coli):

a) Able to accept recombinant DNA (plasmids) through the process of transformation

(b) Able to maintain the structure of the recombinant DNA from one generation to another
(c) Able to amplify (multiply) the gene product of the recombinant DNA

• Modifying enzymes
• Are used to join fragments of DNA. An example of a modifying enzyme is DNA ligase.
 • It catalyzes the formation of the phosphodiester bond (a covalent bond) between the sugar
and phosphate molecules of adjacent nucleotides.
• During the insertion of a target gene into a cloning vector, DNA ligase joins the target gene
and the plasmid to produce a recombinant DNA.

GENETIC ENGINEERING
I. Selective Breeding
• Involves choosing two organisms of the same species and mating them with the
hope of getting the best qualities of each parent to show up in the offspring. This is
done to get specific traits from a desired animal or plant to combine or improve
them for the offspring. However, this takes a long time to process. Genetic
engineering can help speed up that process by going directly to the core.

II. Genetic Engineering

• Direct modification of an organism’s genome, which is the list of specific traits

(genes) stored in the DNA.

• Changing the genome enables engineers to give desirable properties to different

organisms. It produces an organism that has a new trait it would most likely not
have developed on its own.

III. DNA

• In any living thing, the DNA acts as the instruction manual for the body. Certain
genes code for certain proteins and those certain proteins in turn make up parts of
the organism. In a nutshell, the traits of the organism are coded by DNA.

• All living things use the same genetic code which is DNA made from the same 4
bases. A T C G

• An example of a DNA sequence is:

ATCGGACTAG ATGGCCAT GATAGACGA

TAGCCTGATC TACCGGTA CTATCTGCTA

IV. Recombinant DNA Technology

• This process consists of the manipulation as

well as the isolation of specific DNA
segments from different species.

• Scientists can use special enzymes to cut

parts of the DNA of one living organism and
sew them on the DNA of the target. They can choose a specific part of the DNA
and edit it with the desired genome.

• The result is that the living thing has a new gene and a new feature.

V. Genetically Modified Organisms (GMOs)

• Organisms created by genetic engineering are called genetically modified

organisms (GMOs).

• Transgenic organisms contain genes from other organisms.

 Mice + Aequorea victoria Green fluorescent protein (GFP) = Glowing Mice

VI. Short History of GMO Development

• 8000 B.C.: traditional modification methods like selective breeding and

crossbreeding to breed plants and animals with more desirable traits.
• 1866: Gregor Mendel, an Austrian monk, breeds two different types of peas and
identifies the basic process of genetics
• 1940: Plant breeders learn to use radiation or chemicals to randomly change an
organism’s DNA
• 1973: Biochemists Herbert Boyer and Stanley Cohen develop genetic engineering
by inserting DNA from one bacterium into another
• 1974: The GM mice that glow
• 1982: first commercial development of GMOs (insulin-producing bacteria)
• 1994: The first GMO produce created through genetic engineering—a GMO
tomato—becomes available for sale after studies evaluated by federal agencies
proved it to be as safe as traditionally bred tomatoe
• 2003: began to sell GMOs as pets (Glofish)

VII. Applications and Examples of GMOs

• Engineering Plants
o Many of the processed foods that are on the market are genetically modified
crops. They are modified to be bigger and to be resistant to pests and
pesticides.
o One common modified crop is the Bt-corn. A gene from the Bt bacteria is
added so the corn produces a protein that is poisonous to certain insects but
not humans.
o The Venomous Cabbage - Scientists added a
gene for producing scorpion venom to
cabbages to kill caterpillars that eat the crops.

• Engineering Animals
o Bioluminescent Animals
▪ Glowing Mice - It can be used for protein tracking and disease
detection using imaging to identify different types of cells.

o Fast growing salmon – genes from two other fish causes the salmon to
continually produce growth hormones.

o Web-Producing Goats - Spider genes in goats enable the production of

spider silk in goat milk.

• Medicine

o GMO Bacteria

▪ Bacteria are the most common GMOs because their simple structure
permits easy manipulation of their DNA.
 ▪ Humulin – medication used for diabetics is created with genetically
modified bacteria. It can be given to diabetic patients who lack the
insulin they need.

▪ Scientists figured out which section of our DNA codes for insulin
and they also found certain enzymes that cut that gene out. Using
enzymes and heat, they isolate that specific gene and insert it into
the DNA of bacteria. The result is now a bacterium that produces
human insulin. And since bacteria can multiply fast, you can create
a big amount of insulin in a short amount of time.

Genetic engineering is used in the industry of detergents because

scientist have GM enzymes that can break down dirt.

VIII. Advantages and Disadvantages of Genetic Engineering

• Advantages
o Will get improved organisms.
o Can create organisms with traits not previously thought possible.
o Can remove “bad” genes.
o Reduces the chance of getting “undesirable” organisms.
• Disadvantages
o Costly
o Must be performed in a lab with special equipment.
o Ethical issues
o Risk to human health
o Harm to the environment and wildlife

MAIN AREA OF USE

• Medicine
• Agriculture and animal husbandry
• Industry

1. MEDICINE
- Genetic techniques are used in medicine to diagnose and treat inherited human disorders.
- Knowledge of a family history of conditions such as cancer or various disorders may
indicate a hereditary tendency to develop these afflictions.
- Cells from embryonic tissues reveal certain genetic abnormalities, including enzyme
deficiencies, that may be present in newborn babies, thus permitting early treatment.
- Many countries require a blood test of newborn babies to determine the presence of an
enzyme necessary to convert an amino acid, phenylalanine, into simpler products.
- Phenylketonuria (PKU), which results from lack of the enzyme, causes permanent brain
damage if not treated soon after birth.
- Many different types of human genetic diseases can be detected in embryos as young as 12
weeks; the procedure involves removal and testing of a small amount of fluid from around
the embryo (called amniocentesis) or of tissue from the placenta (called chorionic villus
sampling).
• Medical Genetics and Genomic Medicine:
- Applied genetics has revolutionized medical research and healthcare by
aiding in the diagnosis and treatment of genetic disorders. Techniques
such as DNA sequencing, genetic testing, and gene therapy are utilized
to study the genetic basis of diseases and develop personalized treatment
strategies (Ginsburg & McCarthy, 2020).
- Gene therapy is based on modification of defective genotypes by adding
functional genes made through recombinant DNA technology.
 - Bioinformatics is being used to “mine” the human genome for gene
products that might be candidates for designer pharmaceutical drugs.
2. AGRICULTURE AND ANIMAL HUSBANDRY
- Agriculture and animal husbandry apply genetic techniques to improve plants and
animals.
- Breeding analysis and transgenic modification using recombinant DNA techniques
are routinely used.
- Animal breeders use artificial insemination to propagate the genes of prize bulls.
- Prize cows can transmit their genes to hundreds of offspring by hormone treatment,
which stimulates the release of many eggs that are collected, fertilized, and
transplanted to foster mothers.
- Several types of mammals can be cloned, meaning that multiple identical copies
can be produced of certain desirable types.
o Plant geneticists use special techniques to produce new species, such as hybrid grains (i.e.,
produced by crossing wheat and rye), and plants resistant to destruction by insect and
fungal pests.
- Plant breeders use the techniques of budding and grafting to maintain desirable
gene combinations originally obtained from crossbreeding.
- Transgenic plant cells can be made into plants by growing the cells on special
hormones.
- The use of the chemical compound colchicine, which causes chromosomes to
double in number, has resulted in many new varieties of fruits, vegetables, and
flowers.
- Many transgenic lines of crop plants are commercially advantageous and are being
introduced into the market.
3. INDUSTRY
o The brewing industry
- for example, may use geneticists to improve the strains of yeast that
produce alcohol.
o The pharmaceutical industry
- developed strains of molds, bacteria, and other microorganisms high in
antibiotic yield.
- Penicillin and cyclosporin from fungi, and streptomycin and ampicillin
from bacteria, are some examples.
o Biotechnology and Genetic Engineering:
- Applied genetics is fundamental to the field of biotechnology, enabling
the modification of organisms for various purposes. Genetic
engineering techniques are used to produce recombinant proteins,
develop genetically modified organisms (GMOs), and create novel traits
in plants and animals (Nielsen & Nielsen, 2017).
- Biotechnology, based on recombinant DNA technology, is now
extensively used in industry.
- “Designer” lines of transgenic bacteria, animals, or plants capable of
manufacturing some commercial products are made and used routinely.
- Such products include pharmaceutical drugs and industrial chemicals
such as citric acid.
o Forensic Genetics and DNA Profiling:
- Applied genetics plays a crucial role in forensic investigations through
DNA profiling. DNA analysis techniques are used for identification,
paternity testing, and solving criminal cases by comparing DNA
samples collected from crime scenes with those of suspects (Butler,
2021).