2007-2008AP Biology

Chapter 17 Mutations:

Point, Frameshift

and Examples

AP Biology

When do mutations

affect the nextgeneration?

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

AP Biology

Point mutation leads to Sickle cell anemiaWhat kind of mutation?

Missense!

AP Biology

Sickle cell anemia Primarily African Population

recessive inheritance pattern strikes 1 out of 400 African Americans

Link to Animation Link to Discussion on abnormal fiber formation (valine hydroph.)

AP Biology

Mutations Frameshift

shift in the reading frame

changes everything “downstream”

insertions adding base(s)

deletions losing base(s)

Where would this mutation cause the most change:

beginning or end of gene?

AP Biology

Cystic fibrosis Primarily caucasions of European descent

strikes 1 in 2500 births 1 in 25 whites is a carrier (Aa)

normal allele codes for a membrane protein that transports Cl- across cell membrane

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

AP Biology

Effect on LungsChloride channeltransports chloride through protein channel out of cellOsmotic effects: H2O follows Cl-airway

Cl-

H2O

Cl-

H2O

mucus secreting glands

bacteria & mucus build up

thickened mucus hard to secrete

normal lungs

cystic fibrosis

cells lining lungs

Cl- channel

AP Biology

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.

2007-2008AP Biology

What’s the value ofmutations?

Example of Different expressions of codon tables: May have DNA, mRNA or tRNA codons

DNA codons, coding strand, 5’ - 3‘ mRNA codons, 5’ - 3‘

AP Biology

Point mutation leads to Sickle cell anemiaWhat kind of mutation?