1. Chapter 17 Mutations (PART 5)
From Gene to Protein
AP Biology
Ms. Gaynor

2. Mutations
Mutations
Are changes in the genetic material (DNA) of a cell
2 TYPES
1. Point mutations can affect protein structure and function
Are changes in just one base pair of a gene

3. POINT MUTATIONS
The change of a single nucleotide in the DNA’s template strand
Can lead to the production of
an abnormal protein or…
the same protein

4. Point Mutations Point mutations within a gene can are called
Base-pair substitutions
Can results in a mutation (change) that is
harmful
neutral (not harmful or helpful)
beneficial

5. Substitutions 2 TYPES missense (wrong aa)
ONLY 1 wrong aa is added to polypeptide…all the other aa’s are the same
nonsense (prematurely STOP)
The change in DNA leads to an early STOP codon  polypeptide is SHORTEN!!

6. POINT MUTATION ANALOGY…
TEMPLATE: THE CAT ATE THE RAT
POINT MUTATION: THE CAT ATE THE RAT
THE CAT ATE THE BAT  What kind of point mutation is this?
MISSENSE
THE CAT ATE THE XAT  What kind of point mutation is this?
NONSENSE

7. What is the “wobble” effect?
The last base (nucleotide) in a codon is said to be in the WOBBLE position.
codon mutation may encode the same amino acid
Leads to NEUTRAL or SILENT mutations
Not harmful or helpful
SILENT MUTATIONS
Mutation does not change “end result”…change in DNA still makes the SAME amino acid
NO noticeable change occurs
a change from AUU to AUC will still encode Isoleucine

8. What is a neutral mutation?
May or may not affect the resulting protein.
For example, if the codon AAA is mutated to AGA, arginine would be used in the resulting protein instead of lysine
These amino acids are chemically similar and may not have a large effect in the protein or its function
IF this change cause the protein to not function (and be LETHAL to organism) then it is not a neutral mutation but rather a missense mutation

9. Point Mutation Animation

10. 2. Frameshift Mutations Insertions and deletions
Are additions or losses of nucleotide pairs in a gene
produce frameshift mutations
2 TYPES
Insertions
Deletions

11. FRAMESHIFT MUTATION ANALOGY…
TEMPLATE: THE CAT ATE THE RAT
ADDITION of “B” MUTATION: THE CAT ATE THE RAT
THE CAT BAT ETH ERA T  What kind of frameshift mutation is this?
INSERTION
SUBTRACTION of “A” MUTATION: THE CAT ATE THE RAT
THE CAT TET HER AT  What kind of frameshift mutation is this?
DELETION

12. Which is more harmful?
Typically, frameshift mutations are more harmful BUT some point mutations can be LETHAL
Ex: Tay Sachs and Cystic Fibrosis

13. Other Types of Mutations
Inversions
“Flip Flops”
Nucleotides trade places on each strand
Deletions (2+ nucleotides)
Many nucleotides are deleted at once

14. Causes of Mutations Inherited mutations From mom and dad
Spontaneous mutations
occurs during DNA replication
Environmental mutations (Mutagens)
physical or chemical agents that can cause mutations
Ex: Sun, viruses, chemicals

15. Belgian Blue Cattle (so beefy….)
The Belgian Blue has a natural mutation in myostatin gene, which codes for protein that inhibits muscle development and fat deposition (creates very lean meat).

17. Piedmontese cattle (still so beefy…)