Lecture 10

Question 1

What is a mutation?

Answer 1

heritable change in the DNA; the process by which such a change occurs

Question 2

What is a mutant?

Answer 2

a cell/organism with a mutation

Question 3

How do mutations occur?

Answer 3

there is no repair or incorrect DNA repair to damaged base pairs

Question 4

Are all mutations spontaneous?

Answer 4

no. Some are induced (i.e. UV)

Question 5

What is a mutagen?

Answer 5

physical or chemical agent that raises the mutation frequency above the spontaneous rate

Question 6

What happens in the deamination of cytosines?

Answer 6

A spontaneous reaction turns cytosine to uracil (water kicks out an amine group)

A GC bp turns into a GU bp

during the next round of DNA replication, uracil behaves like thymine, and pairs with adenine

ends up with GC AU

Then GC AU turns into GC GC and AT AU

Therefore, the consequence is that GC turns to AT

Question 7

What is base excision repair (BER)?

Answer 7

1) DNA repair enzymes recognize damaged bases and remove them

2) other DNA repair enzymes replace the DNA (i.e. sugar and P, then dCTP with DNA pol and DNA ligase)

Question 8

Give an example of and enzyme used in BER. What does it do?

Answer 8

uracil DNA glycosylase (removes uracil)

Question 9

DNA polymerase misaligns in repeat-rich regions, causing small insertions or deletions (indels). What is this called?

Answer 9

Replication slippage

Question 10

What are the two types of spontaneous mutations?

Answer 10

base pair substitutions

indels

Question 11

What are the two DNA repair systems learned?

Answer 11

BER: fixes damaged nucleotides

NHEJ: fixes damaged chromosomes

Question 12

What is the result of deamination of cytosines?

Answer 12

GC to AT bp mutation