Transcript Chapter 17 Mutations/Deletions Examples

AP Biology
Chapter 17
Mutations:
Point,
Frameshift and
Examples
2007-2008
Mutations

Point mutations
single base change
 base-pair
substitution


silent mutation
 no amino acid change
 redundancy in code
(wobble effect)

missense
 change amino acid

nonsense
 change to stop codon
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When do mutations
affect the next
generation?
Point mutation leads to Sickle cell anemia

What kind of
mutation?
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Missense!
Sickle cell anemia

Primarily African Population
 recessive inheritance pattern
 strikes 1 out of 400 African Americans


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Link to Animation
Link to Discussion on abnormal fiber formation (valine hydroph.)
Mutations

Frameshift

shift in the reading
frame


insertions


adding base(s)
deletions

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changes everything
“downstream”
losing base(s)
Where would this mutation
cause the most change:
beginning or end of gene?
Cystic fibrosis

Primarily caucasions of European descent
 strikes 1 in 2500 births


normal allele codes for a membrane protein
that transports Cl- across cell membrane

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



1 in 25 whites is a carrier (Aa)
defective or absent channels limit transport of Cl- (& H2O)
across cell membrane
thicker & stickier mucus coats around cells
mucus build-up in the pancreas, lungs, digestive tract &
causes bacterial infections
without treatment children die before 5;
with treatment can live past their late 20s
Quick intensive animation (must see)
Link to Animated Discussion
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Chloride channel
Effect on Lungs
normal lungs
airway
Cl-
transports chloride through
protein channel out of cell
Osmotic effects: H2O follows ClCl- channel
H 2O
cells lining
lungs
cystic fibrosis
ClH 2O
bacteria & mucus build up
thickened mucus
hard to secrete
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mucus secreting glands
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Notice that after CTT is removed,
the AT T joins and still makes the
same amino acid (ATC and ATT both
are DNA codons for isoleucine, but
the PHE is omitted) example of
Silent Mutation PLUS DELETION.
What’s the value of
mutations?
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2007-2008
Example of Different expressions of codon tables:
May have DNA, mRNA or tRNA codons
DNA codons, coding strand, 5’ - 3‘
mRNA codons, 5’ - 3‘
Point mutation leads to Sickle cell anemia

What kind of
mutation?
AP Biology