Mutations

Question 1

What is a mutation?

Answer 1

A heritable change to the DNA sequence of an organism

Question 2

What is a wild-type allele?

Answer 2

The most prevalent allele in a population

Question 3

What are 4 ways to classify mutations?

Answer 3

Where it came from, effects at a molecular level, effects on the phenotype, effects on gene product activity

Question 4

Can mutations be spontaneous?

Answer 4

Yes, but they are rare because of proofreading mechanisms and repair find and fix most of them

Question 5

What is a mutagen?

Answer 5

A substance that induces a mutation

Question 6

What are the 3 classes of mutagens?

Answer 6

Chemical, physical, biological

Question 7

What type of mutations are generated by chemical mutagens?

Answer 7

Point mutations

Question 8

What are the 3 major mechanisms used by chemical mutagens to generate mutations?

Answer 8

Base modification, intercalating into the DNA backbone, base analogs

Question 9

How does base modification create mutations?

Answer 9

Adding modifications to bases changes their H bonding properties, so they base pair with something else

Question 10

What mechanism does EMS cause mutations through?

Answer 10

Base modification. Changes guanine to O-6-ethylguanine which base pairs with a T instead of C. Causes base pair substitutions

Question 11

How does backbone intercalation create mutations?

Answer 11

Alters the physical structure of DNA and stalls replication, leading to the incorporation of incorrect bases

Question 12

What mechanism do acridine and ethidium bromide cause mutations through?

Answer 12

Backbone intercalation. They are large, planar, multi-ringed molecules that in between the bases and disrupt the structure of DNA. Cause indels

Question 13

How do base analogs create mutations?

Answer 13

They mimic normal bases and get incorporated during replication, but they base pair with the wrong thing

Question 14

What mechanism does 5-bromouracil cause mutations through?

Answer 14

It mimics a thymine, so gets incorporated during DNA replication. The enol form will base pair with a G instead of an A

Question 15

What types of mutations are generated by physical mutagens?

Answer 15

Large scale double strand breaks that result in deletions, inversions, or translocations. Pyrimidine dimers

Question 16

What is ionizing radiation? What type of DNA damage and mutations does it cause?

Answer 16

Fast, high energy forms of radiation. Includes gamma rays, x-rays, fast neutrons. They create double strand breaks. Can result in deletions, inversions, or translocations

Question 17

What is non-ionizing radiation? What type of DNA damage and mutations does it cause?

Answer 17

Lower energy radiation that doesn’t cause strand breaks, aka UV light. Causes pyrimidine dimers

Question 18

What are the two types of deletions that could be caused by ionizing radiation? Which one is more common?

Answer 18

Terminal (end of the chromosome) and interstitial (inside a chromosome). Terminal is more common because it only requires one strand break

Question 19

What type of mutations are caused by biological mutagens?

Answer 19

Insertions and deletions

Question 20

What are transposons?

Answer 20

Moveable pieces of DNA that are endogenous to every eukaryotic genome

Question 21

What is an advantage to using transposons?

Answer 21

Cloning the affected gene is very easy, since we know the sequences of the transposon and use restriction enzymes to figure out where in the genome the mutation occurred

Question 22

How can transposons generate deletions?

Answer 22

If it is removed, it will take a bit of the surrounding DNA when it leaves and cause a small deletion

Question 23

What are the two mechanisms by which transposons generate mutations?

Answer 23

Replicative transposition and non-replicative transposition

Question 24

What is replicative transposition?

Answer 24

The original transposon gets copied, and the copy moves to a new location, but the original stays put and does not generate a deletion. Proceeds through an RNA intermediate (copy and paste)

Question 25

What is non-replicative transposition?

Answer 25

The original transposon gets cut out from where it was and gets moved to another location. Creates a deletion where it originally was