comparison DNA RNA
Deoxyribonucleic Ribonucleic
Acid Acid
Sugar Sugar=deoxyribose Sugar= ribose
Contains 1 more
H atom than
deoxyribose
Strands Double stranded Single stranded-
a single strand
of nucleotides
Bases Nitrogen bases: Nitrogen bases:
ATCG AUCG
U=Uracil
What step in protein synthesis is
this?
http://www.odec.ca/projects/2004/mcgo4s0/public_html/t3/mRNA%20to%20protein.gif
AMINO ACID
•building blocks
of proteins
Explain the steps in protein
synthesis.
http://stemcells.nih.g
ov/info/scireport/im
ages/figurea6.jpg
PROTEIN SYNTHESIS
• Transcription= process of making RNA
from DNA
• Translation= RNA directions are used to
make a protein from amino acids
• DNARNA Protein
• Transcription Translation
Cytoplasm on
nucleus
ribosome
Try this example.
• Using the following DNA sequence, what
would be the complementary RNA
sequence?
• ATC CGT AAT TAT GGC
Roles of RNA and DNA
• The cell uses the vital DNA “master plan”
to prepare RNA “blueprints.”
• The DNA molecule remains within the
safety of the nucleus, while RNA molecules
go to the protein-building sites in the
cytoplasm—the ribosomes.
Mutations
What Are Mutations?
• Changes in the
nucleotide sequence of
DNA
• May occur in somatic
cells (aren’t passed to
offspring)
• May occur in gametes
(eggs & sperm) and be
passed to offspring
Mutations (12-4)
• Mutation – changes in the
genetic material (like mistakes
in copying or transcribing)
Are Mutations Helpful or
Harmful?
• Mutations happen
regularly
• Almost all mutations are
neutral
• Chemicals & UV
radiation cause
mutations
• Many mutations are
repaired by enzymes
Are Mutations Helpful or
Harmful?
• Some type of skin
cancers and leukemia
result from somatic
mutations
• Some mutations may
improve an organism’s
survival (beneficial)
Types of Mutations
Types of Mutations
Chromosomal Gene Mutations -
Mutations - Involve Mutations that produce
changes in the number or changes in a single
structure of chromosomes. gene.
Ex. Downs Syndrome
Chromosome Mutations
• May Involve:
– Changing the
structure of a
chromosome
– The loss or
gain of part of
a chromosome
Chromosome Mutations
• Five types exist:
– Deletion
– Inversion
– Translocation
– Nondisjunction
– Duplication
Deletion
• Due to breakage
• A piece of a
chromosome is lost
Inversion
• Chromosome segment
breaks off
• Segment flips around
backwards
• Segment reattaches
Duplication
• Occurs when a
gene sequence is
repeated
Translocation
• Involves two
chromosomes that
aren’t homologous
• Part of one
chromosome is
transferred to
another chromosomes
Translocation
Nondisjunction
• Failure of
chromosomes to
separate during
meiosis
• Causes gamete to
have too many or
too few
chromosomes
Chromosome Mutation
Animation
QUICK QUIZ!
1. CHROMOSOMES
FAILED TO SEPARATE
DURING MEIOSIS
________________
NONDISJUNCTION
INVERSION
DUPLICATION
DELETION
•A PIECE OF THE
CHROMOSOME IS
LOST DUE TO
BREAKAGE.
Gene Mutations
• Change in the
nucleotide sequence
of a gene
• May only involve a
single nucleotide
• May be due to copying
errors, chemicals,
viruses, etc.
Types of Gene Mutations
• Include:
– Point Mutations
– Substitutions
– Insertions
– Deletions
– Frameshift
Point Mutation
• Change of a single
nucleotide
• Includes the
deletion, insertion, or
substitution of ONE
nucleotide in a gene
Point Mutation/Missense
mutation
• Sickle Cell
disease is the
result of one
nucleotide
substitution
• Occurs in the
hemoglobin gene
Point Mutations: Silent
1. Silent mutation: a base is changed, but
the new codon codes for the same amino
acid. ( typically it is the third letter in the
codon) Not all mutations are harmful.
Original
leading to a silent mutation
mRNA
Protein
Frameshift Mutation
• Inserting or deleting
one or more nucleotides
• Changes the “reading
frame” like changing a
sentence
• Proteins built
incorrectly
Frameshift Mutation
• Original:
– The fat cat ate the wee
rat.
• Frame Shift (“a”
added):
– The fat caa tet hew
eer at.
Amino Acid Sequence
Changed
Gene Mutation
Animation
Genetic Disorders
1.Recessive Disorders
Happens when a child
receives two
defective genes from
each parent.
A person who
receives one
defective recessive
genes is called
carrier.
Recessive Disorders
a. Sinkle Cell anemia: a
genetic blood disorder.
A person who inherits
two defective genes
will have abnormally
shaped red blood cells
May die at an early
stage.
Recessive Disorders
b. Tay –Sachs:
characterized by
the lack of an
important chemical
in the brain.
die in the first
five years
Recessive Disorders
c. Phenylketonuria or PKU: a
rare genetic disorder that can
cause serious mental
retardation.
Cannot breakdown
phenylalanine that it builds
up in the body, in which
the brain is affected.
Can be treated through a
special diet.
Recessive Disorders
d. Cystic fibrosis: a
disease in which some
glands produce too much
mucus that it clogs and
damage the lungs.
Fatal among children
because it is difficult
for them to breathe.
Genetic Disorders
2.Sex-linked Disorder
Common in men
because they have
only one X
chromosomes.
Color blindness
and hemophilia.
Genetic Disorders
3. Human Genetic Syndrome
a. Cri du cat
Deletion of part of the
short arm of
chromosomes 5
A French term
Have a wide set-eyes,
small head and jaw
High pitched cries
(sounds like cat)
Genetic Disorders
3. Human Genetic Syndrome
b. William Syndrome
Loss of a segment in
chromosome 7.
Have large ears and
facial expression
that make them
look live elves.
Genetic Disorders
3. Human Genetic Syndrome
c. Down Syndrome (trisomy
21)/ Mongolsim
Extra copy of
chromosome 21
Had a distinctive
physical appearance
Cause mental
retardation (mild/
severe)
Genetic Disorders
4. Edward Syndrome (trisomy 18)
Extra number chromosome 18.
Shows mental retardation and
physical abnormalities.
Can live beyond one year.
99% die in infancy.
clenched hands and over lapping
fingers
Genetic Disorders
5. Patau Syndrome (trisomy 13)
Extra copy of chromosome 13
90% die in infancy
Severe mental retardation to
those who survived
Genetic Disorders
6. Klinefelter’s Syndrome
(XXY)
Usually sterile
Tend to have longer arms
and legs and taller than
their peers
Often shy and quiet
Have speech delay
Genetic Disorders
7. Turner’s Syndrome
Have 45 chromosomes
X instead of XX or XY
Female sexual characteristics are
present bur underdeveloped.
96-98% do not survive birth
Have no menstruation, have narrow
hips, breast are not developed,
have a broad shoulder and neck and
have a short stature.
Genetic Disorders
8. Jacob’s Syndrome:
Terminal 11 deletion disorder.
Very rare disorder
Have normal intelligence or mild
retardation with poor or excessive
language skills
Most have bleeding disorder called
“Paris –Trousseau Syndrome”
Causes of Mutation
• Smoking can raise
risks of genetic
mutation
• Effect of old age on
offspring
• Chemotherapy
Gene Regulation
The expression of genes can also be
influenced by environmental factors such
as temperature, light, chemicals, etc.
Human Karyotype
• Karyotypes may reveal the
gender of a fetus or test for
certain defects through
examination of cells from uterine
fluid – a procedure called
amniocentesis – or through
sampling of placental
membranes
Significance of Mutations
• Many mutations have little or
no effect on the expression of
genes.
• Mutations may be harmful and
may be the cause of many
genetic disorders and cancer.
• Source of genetic variability in
a species (may be highly
beneficial).
Beneficial Mutations
• Beneficial mutations may produce proteins
with new or altered activities that can be
useful to organisms in different or changing
environments.
• Plant and animal breeders often take
advantage of such beneficial mutations.
– The condition in which an organism has extra
sets of chromosomes is called polyploidy.
• Often larger and stronger than diploid
plants, but not beneficial in animals.
Genetic engineering
• When DNA from two different species are
joined together, it is called recombinant
DNA. This process uses restriction
enzymes to cleave one organism’s DNA
into fragments and other enzymes to
splice the DNA fragment into a plasmid
or viral DNA. Transgenic organisms are
able to manufacture genetic products
foreign to them using recombinant DNA.
