Download Ch. 8 Mutations

Mutations
Aka, Pobody’s
Nerfect
Could you imagine copying the New York City
phone book perfectly? Do you think you might
make a few errors?
The Human Genome (all of our DNA and genes)
contains 3.2 billion base pairs.
During DNA Replication, DNA makes an error
every 100,000 base pairs and repairs it to an
average of one error every 10 billion base
pairs.
That’s an average of 0.31 base pairs each time
DNA is replicated.
What is a mutation?
A mutation is any change in an organism’s
DNA
There are two types of mutations
a) Gene mutation. Influences usually only
one gene
b) Chromosomal mutations. Changes in the
structure of a chromosomes or the
number of chromosomes
GENE MUTATIONS
There are two types of Gene mutation
Gene mutations are inheritable and can be
passed on to the next generation
a) Point mutation
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One nucleotide is changed or substituted
for another base
These are usually fixed during replication
These are usually the driving forces of
evolution
–
The difference between our hemoglobin
protein (contains iron which carries the
oxygen in our blood) and that of a gorilla is
one amino acid in a chain of 146.
THE FAT CAT ATE THE RAT
– Change the C in CAT to a B.
– THE FAT BAT ATE THE RAT
– Did this point mutation drastically change the
meaning of the sentence?
– This is a missense mutation. These are the type
that drive evolution
• If DNA reads: A T G G T C G A T T G G CAA
• mRNA:
U A C C A G C U A AC C GUU
• Protein:
Tyrosine - Glutamine – Leucine -Threonine – Valine
• But if mRNA: U A C C A G C A A AC C GUU
• Protein:
Tyrosine – Glutamine – Glutamine – Threonine – Valine
Only 1 Amino acid in the sequence was altered.
Sickle Cell Anemia
Compare the DNA Sequence for Normal Red Blood cells
How does the DNA Sequence for Sickled red blood cells compare?
What was changed?
The T in the normal sequence was changed to an A, causing the
RBC’s to have a different structure.
These sickled RBCs will not flow easily through the blood vessels
and will also not carry as much oxygen, thus the anemia part of
its name
Where in the World is Sickle Cell Anemia?
• The highest incidents of SCA is found in Africa, Saudi
Arabic and India.
• 1/500 people of African decent are carriers of the
gene for SCA.
• 1/12 African Americas carry the gene.
THE FAT CAT ATE THE RAT
Change the C in CAT to a K.
THE FAT KAT AT THE RAT
Has this changed the statement much?
This is a silent mutation. The proper protein
will still be produced
b. Frameshift mutations.
Involve the insertion or deletion of a nucleotide
in a DNA sequence.
THE FAT CAT ATE THE RAT
Take out the F in FAT and then shift all the other
letters over to still make a word with 3 letters.
THE ATC ATA TET HER AT
What is that? This makes no sense at all
These are the mutations that have the most
drastic effect on the organism and will lead to a
protein not being produced properly
• If DNA reads: A T G G T C G A T T G G CAA
• mRNA:
U A C C A G C U A AC C GUU
• Protein:
Tyrosine - Glutamine – Leucine -Threonine – Valine
• BUT if mRNA: U A C C A G U A A C C G U U _
• Protein: Tyrosine - Glutamine STOP!!!
• The entire sentence makes no sense. The protein
formed would be totally different
Chromosomal Mutations
• Involve changes in the number and structure
of the chromosomes.
• Could change the location of genes on the
chromosomes or the number of copies of
some of the genes.
• Deletions – part of a chromosome is missing
• Duplications – Extra copies of genes are inserted
Cri-du-Chat Syndrome
Caused by a small
deletion on
chromosome #5
1/20,000 children
Breathing, talking,
learning, heart
and walking
problems
Extra or Missing Chromosomes
During Meiosis
(production of gametes
with half the normal
number of
chromosomes)
sometimes
chromosomes don’t
separate as they should
Results in missing or extra
chromosomes
Trisomy 21 is an example
What can cause mutations?
Mutations happen all the time naturally.
Sometimes though, mutations are more likely to
happen with certain environmental agents
(called Mutagens) such as:
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UV radiation from the sun
Pesticides and other toxic compounds
Asbestos
Cigarettes – causes 400,000 deaths in US/year
Marijuana