BIO1 5
Introduction to
Genetics
VER A MAR IE MIR ABUEN O
LIST OF KEY CONCEPTS
Overview of • The beginning of Genetics
• Terminologies used in this topic
this topic • The Scope of Genetics
What is
Genetics?
THE S CI ENCE O F COMING INTO
BEING
The term Genetics was introduced by Bateson
in 1906. It was derived from the Greek word
“Gene” which means “to become” or “to grow
into”
What is
Genetics?
THE S CI ENCE O F COMING INTO
BEING
The branch of biology deals with heredity,
especially the mechanisms of heredity
transmission and the variation of inherited
characteristics among similar or related
organisms.
GENETICS is the branch of biological
sciences that deals with the transmission of
characteristics from parent to offspring.
History of GENETICS
19TH CENTU RY
• In 1859, Charles Darwin gave the theory of
evolution.
• How organisms evolve with time.
• He visited the Galapagos Island to study
finches.
History of GENETICS
GREGOR MENDEL
“Father of Genetics”
• He experimented on a pea plant and
discovered how traits are passed from one
generation to the next.
• Laws of Mendel
- “Law of Independent assortment”
- “Law of Segregation”
History of GENETICS
FREI DRICH MIESCHER, 1869
• He had successfully isolated the “nuclein”
inside the nuclei of the human white blood
cells.
• Not long after, he was able to prove that
“nuclein” is present in other cells as well.
History of GENETICS
ERNST HAECKEL, 1871
• A German Zoologist and a naturalist.
• His experiments proved that the genetic
material is indeed located in the nucleus.
History of GENETICS
During the 20th century to current,
• 1902: Walter Sutton and Theodore Boveri postulated the
Chromosomal theory which describes that chromosomes carry
the cell’s genetic material (gene).
• 1905: Nettie Stevens observed the sex chromosomes X and Y.
• In the same year, Thomas Morgan discovered the sex linked
inheritance of the white eye traits in fruit flies (Drosophila
melanogaster).
• 1905: William Bateson coined the term “genetics” from the Greek
word “genno” which means “to give birth” in order to describe the
study of inheritance and variation.
• 1909: Bateson published his book entitled “Mendel’s Principles of
Heredity.
History of GENETICS
During the 20th century to current,
• 1910: Reginald Punnett and William Bateson discovered the
science of genetic linkage. They also coined the term “epistasis:
to describe the interaction between two different traits.
• 1944: The experiments of Oswald Avery and his colleagues proved
that the DNA is the molecule responsible for inheritance.
History of GENETICS
During the 20th century to current,
• 1953: James Watson and Francis Crick
The three-dimensional and double helix model of the DNA was
proposed by James Watson and Francis Crick. Such discovery also
paved the way for the formation of basis of other fields like cell
biology and biotechnology. In the same year, the process of DNA
replication was discovered.
History of GENETICS
During the 20th century to current,
• Frederick Sanger, 1977
In 1977, a british biochemist named Frederick
Sanger introduced the process of sequencing the
genome (set of genes of an organism) of a
bacteriophage. Later, scientists have done it in other
organisms as well and he is The first to determine the
amino acid sequence of insulin.
History of GENETICS
During the 20th century to current,
• 1983: Kary Mullis invented the process called Polymerase Chain
Reaction. In this technique, a segment of the DNA is amplified
until millions of copies are produced in just a short period.
• 1990: In this year, the Human Genome Project was started.
• 1996: In this year, Ian Wilmut and Keith Campbell have
successfully cloned DOLLY the sheep. Dolly was the first
mammal to be cloned from an adult cell.
History of GENETICS
• 2003: The Human Genome project was completed in 2003. The
results of the project showed for the first time the complete
genetic make up for building a human being.
• And the work goes on.
TERMINOLOGIES
What is DNA?
• DNA (deoxyribonucleic acid)
carries the genetic information
in the body’s cells.
• DNA is made up of four similar
chemicals (called bases and
abbreviated A, T, C, and G)
repeated over and over in pairs.
• Adenosine, Thymine, Cytosine,
Guanine
TERMINOLOGIES
What is a Gene?
• A gene is a distinct portion of a
cell’s DNA.
• Genes are coded instructions
for making everything the body
needs, especially proteins.
• Human beings have about
25,000 genes. Researchers have
discovered what some of our
genes do, and have found that
are associated with disorders
• Gene holds the information to (such as cystic fibrosis or
maintain their cells and pass Huntington’s disease). There
genetic traits to offspring. are, though, many genes whose
functions are still unknown.
TERMINOLOGIES
What is an Allele?
• Alleles are pairs or series of genes on a
chromosome that determines the
hereditary characteristics. An example
of an allele is the gene that determines
hair color.
• An allele is located at a fixed position on a
chromosome. Chromosomes exist in pairs, so
organisms have two alleles for each gene—one
on each chromosome in the pair. Because each
chromosome in the pair comes from a
different parent, organisms inherit one allele
for each gene from each parent. The two
alleles inherited from parents can be the same
(homozygous) or different (heterozygous). This
article explains the key difference between
gene and allele.
TERMINOLOGIES
What is an Allele?
• A dominant allele produces a
dominant phenotype in individuals
with one copy of the allele, which can
come from just one parent.
• For a recessive allele to produce a
recessive phenotype, the individual
must have two copies, one from each
parent.
• An individual with one dominant and
one recessive allele for a gene will have
the dominant phenotype. They are
generally considered “carriers” of the
recessive allele: the recessive allele is
there, but the recessive phenotype is
not.
TERMINOLOGIES
What is a Phenotype?
• A phenotype (from Greek phainein,
meaning "to show", and typos,
meaning "type") is the composite of an
organism's observable characteristics
or traits, such as its morphology,
development, biochemical or
physiological properties, phenology,
behavior, and products of behavior
(such as a bird's nest).
INSIDE THE CELL
SCOPE/APPLICATIONS OF
GENETICS
Genetics has scope/role in the
following fields:
1.GENETICS AS BASIS OF BIOLOGI CA L SCIENCES;
Provide foundation for biological studies. Laws of inheritance help
us to understand the principles of embryology, population,
taxonomy, evolution and ecology.
2. ROLE O F GENETICS I N FOOD PRODUCTION
Rules of genetics help to introduce new verities of plants and
livestock.
Genetics has scope/role in the
following fields:
3. DISEA SE CONTROL
Gene therapy help to cure many genetics based diseases.
4. CONSERVATION OF WILDLIFE
Conservation of wildlife can be achieved in one way by conserving
the germplasm of endangered species.
5. GENETIC ENGINEERING/BIOTECHNOLOGY:
Genetic Engineering has many applications including
a. Development of transgenic crops.
b. Gene therapy
c. Improvement in Food production
d. Control of Genetic Diseases
e. Gene Mapping
Genetics has scope/role in the
following fields:
6. BEHAVIORAL GENETICS
It studies the influence of varying genetics on animal behavior.
7. CLINICAL GENETI CS
There are several genetic disorder exist physicians are trained to
diagnose and treat.
8. MO LECU LA R GENETICS
It focus on structure and function of gene.
Genetics has scope/role in the
following fields:
9. POPU LATION AND ECOLOGI CA L GENETICS
Population and ecological genetics are closely related subfields of
genetics. Population genetics is the study of distribution and change
in allele.
10. GENOMICS
It allows the study of large scale genetic pattern
i.e GENOMIC SEQUENCE
MENDELIAN PATTERNS OF
INHERITANCE
FATHER OF GENETICS
GREGOR JOHANN MENDEL (1822-1884)
Austrian monk
Born in 1822 near Brunn in Austria, in a poor family
Studied the inheritance of traits in the garden pea.
Published his theory in 1866 “Experiments on Plant Hybrids”
In 1900, the work of Mendel was independently rediscovered by
• Hugo de Vries (Holland)
• Carl Correns (Germany)
• Erich Tshermak (Austria)
PEA PLANTS are a
GOOD MODEL
• Peas are easy to grow
• They reproduce quickly
• Emasculation and pollination quite
easy
• They are capable of self fertilization
Mendelian’s Pattern of
Inheritance
TRUE BREEDI NG
Organisms that are homozygous for genes. This means
that both alleles are the same, so PP or TT as opposed
to Pp or Tt. When true breeding organisms are
crossed, all progeny will have the same phenotype as
the parents.
HYBR IDS
Offspring of two different varieties
HYBR IDIZATION
The process of cross-fertilization also called as genetic
cross.
P generation
True breeding parents (P for parental) and their hybrid
offspring are called the F1 generation (F for filial, from
latin word for “son”). When F1 plants self-fertilize or
fertilize each other, their offspring are the F2
generation.
Quick Question.
IF TRUE-BREEDING WHI TE AND TRU E -BREEDING PURPLE
PEAS WERE CROSS ED, WHAT TERMS WOULD BE U SED TO
DESCRIBE THEIR OFFS PRI NG?
Quick Question.
IF TRUE-BREEDING WHI TE AND TRU E -BREEDING PURPLE
PEAS WERE CROSS ED, WHAT TERMS WOULD BE U SED TO
DESCRIBE THEIR OFFS PRI NG?
Answer: Their offspring would be F1 generation, and
they would be called hybrids.
Important terms to remember!
GENE
Unit of inheritance usually occurring at specific locations, or loci, on a
chromosome. Physically, a gene is a sequence of DNA bases that specify the
order of amino acids in a protein. Genes are responsible for hereditary traits
in plants and animals.
ALLELE
An alternative form of a gene that
occurs at the same locus on
homologous chromosomes
Important terms to remember!
DOMINANT ALLELE
An allele that masks the presence of a recessive allele in the phenotype. Dominant alleles for a
trait are usually expressed if an individual is homozygous dominant or heterozygous.
RECESS IVE ALLELE
An allele that is masked in the phenotype by the presence of a dominant allele. Recessive alleles
are expressed in the phenotype when the genotype is homozygous recessive.
The uppercase letters are used to
denote dominant alleles, whereas
the lowercase letters are used to
denote recessive alleles.
Important terms to remember!
HOMOZYGOU S
Having the same allele at the same locus on pair of homologous chromosomes. Homozygous also
refers to a genotype consisting of two identical alleles of a gene for a particular trait. Individuals
who are homozygous for a trait are reffered to as homozygotes.
Important terms to remember!
HETEROZYGOUS
a genotype consisting of two different alleles of a gene for a particular trait (Bb). Individuals who
are heterozygous for a trait are referred to as heterozygotes.
Mendel’s Laws of Inheritance
1.LAW OF DOMINANCE
2.LAW OF SEGREGATION
3.LAW OF INDEPENDENT ASSORTMENT
Important terms to remember!
GENOTYPE
refers to an individual’s the “genetic potential” - what kind of genes he or she carries.
PHENOTYPE
(from the Greek word “pheno” meaning “to show”) refers to teh traits an individual actually
shows.
Important terms to remember!
MONOHYBRID CRO SS
is one in which both parents are heterozygous (or a hybrid) for a single (mono) trait. The trait
might be petal color in pea plants. When conducting crosses, the first generation is called P (or P0),
the second generation is F1 (F is for filial), and the next generation is F2.
Figure 1: (a) A true-breeding line (b) A monohybrid cross produced by mating two different pure-
breeding lines.
Important terms to remember!
PU NNET SQ UA RE
is a matrix in which all of the possible gametes produced by one parent are listed along one axis,
and the gametes from the other parent are listed along the other axis. Each possible combination
of gametes is listed at the intersection of each row and column. Punnett squares can also be used
to calculate the frequency of types offspring that are expected.
Figure 2: Top: A Punnett square shows the possible offspring of a monohybrid cross between Pp and Pp parents.
https://youtu.be/gWSBbFC0q5I
Law of Dominance
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in
the next generation. All offspring will be hybrid for a trait and will have only the dominant trait
express the phenotype. The phenotype trait that is NOT expressed in the hybrid is called recessive.
Law of Dominance
Genotypic Ratio: 1:2:1
Phenotypic Ratio: 3:1
EXAMPLE
1. In guinea pigs, short hair, S is dominant to long hair, s. Complete the following
Punnet squares according to the directions given. Then, fill in the blanks beside
each Punnet square with the correct numbers
a. One guinea pig is Ss and one is ss..
Expected number of offspring:
Short hair:
Long hair:
b. Both guinea pigs are heterozygous for short hair
Expected number of offspring:
Short hair:
Long hair:
EXAMPLE
1. In guinea pigs, short hair, S is dominant to long hair, s. Complete the following
Punnet squares according to the directions given. Then, fill in the blanks beside
each Punnet square with the correct numbers
a. One guinea pig is Ss and one is ss..
Expected number of offspring:
Short hair: 2 (SS or Ss)
Long hair: 2 (ss)
b. Both guinea pigs are heterozygous for short hair
Expected number of offspring:
Short hair: 3
Long hair: 1
EXAMPLE
2. Hornless (H) in cattle is dominant over horned (h). A homozygous hornless bull is
mated with a homozygous horned cow. What will be the genotype and phenotype
for the first generation?
EXAMPLE
2. Hornless (H) in cattle is dominant over horned (h). A homozygous hornless bull is
mated with a homozygous horned cow. What will be the genotype and phenotype
for the first generation?
Law of Segregation
Mendel’s LAW of SEGREGATION states that TWO ALLELES of a GENE that are found on a
chromosome pair separate, with the offspring receiving one from the mother and one from
the father. According to Mendel’s Law, the two alleles act in a segregated fashion and do not
mix or change each other.
These two alleles will be separated from each other during meiosis. Specifically, in the
second of the two cell divisions of meiosis. Specifically, in the second of the two cell divisions
of meiosis the two copies of each chromosome will be separated from each other, causing
the two distinct alleles located on those chromosomes to segregate from one another.
This law is also referred to as LAW OF PURITY OF GAMETES.
Law of Segregation
The Law of Independent Assortment
It states that inheritance of one character is always independent of the inheritance of other
characters within the same individual.
Law of independent assortment is based on DIHYBRID CROSS.
The alleles of two more genes get sorted into gametes independent of each other. The allele
received for one gene does not influence the allele received for another gene.
Genes linked on a chromosome can rearrange themselves through the process of crossing-
over. Therefore, each gene inherited independently.
The Law of Independent Assortment
BOARD WORK
Monohybrid Cross
1.In mice, black fur (B) is dominant over brown fur (b). A homozygous black-
furred mouse (BB) is crossed with a heterozygous black-furred mouse (Bb).
a. Identify Parental Genotypes
b. Set Up the Punnet Square
c. Write the Genotype’s and Phenotype’s ratio
2. In rabbits, black fur (B) is dominant over white fur (b), and long ears (L) are
dominant over short ears (l). Two rabbits with the genotype BbLl are crossed.
What is the phenotypic ratio of the offspring?
THE CHEMISTRY
OF LIFE
GENE EDITING ON HUMANS
ELEMENTS OF
LIFE
• 96% OF THE HUMAN BODY
IS MA DE UP O F:
OXYGEN
CARBON
HYDROGEN
• Calcium, phosphorus, sulfur,
NITROGEN potassium, and other elements
amounts
Organic Molecules
CARBON BONDING
FOUR GROUPS OF ORGANIC MOLECULES
• CARBOHYDRATES • LIPIDS
Fuel for cell functions Stored energy and membrane
structure
• NUCLEIC ACIDS • PROTEINS
many cell functions
genetic information
Carbohydrates
• FUEL FOR CELL FUNCTIONS
• MADE UP OF SACCHARIDES
( SUGARS)
1. Glucose
2.Sucrose
3.Dextrose
4.Maltose
5.Lactose
6.Fructose
7. Amylose
8.Cellulose
... and many more
CARBOHYDRATES
CARBOHYDRATES
(DISSACCHARIDES)
CARBOHYDRATES
COMMON DISACCHARIDES
CARBOHYDRATES
PLANT POLYSACCHARIDES
CARBOHYDRATES
ANIMAL POLYSACCHARIDES
LIPIDS
FATTY ACIDS
STORED ENERGY LIPIDS
CELL MEMBRANE LIPIDS
STEROIDS
NUCLEIC ACIDS
NUCLEIC ACIDS
(Nucleotide Structure)
DNA
Deoxyribonucleic acid
• Double-stranded helix
• Has the sugar DEOXYRIBOSE
• Forms CHROMOSOMES
- carry genetic information
• Uses four nucleotide bases
- ADENINE (A)
- GUANINE (G)
- CYTOSINE (C)
- THYMINE (T)
RNA
PROTEINS
AMINO ACIDS
Protein Structure
Protein Structure
PROTEINS
SUMMARY
