Exam 3 Mutations

Question 1

what does induced mutations mean and the 6 types

Answer 1

induced mutations = causative agents from environment

1. base anologs
2. alkylating agents
3. intercalcating agents
4. adduct-forming agents
5. UV light
6. ionizing radiation

Question 2

what does base analog do?

Answer 2

induced mutation where a tautomer is present to cause a base pair eg uracil (BrdU) can base pair with either A or G

Question 3

what does alkylating agents do?

Answer 3

addition of a butyl groups that change H bonding potential ex mustard gas

Question 4

mustard gas causes what type of base pairing

Answer 4

now preferably H bonds guanine with T rather than C; when DNA is next replicated, half of our template will be different from original

Question 5

intercalating agents act where

Answer 5

induced mutation

slide in between DNA rungs of the ladder

Question 6

adduct-forming agents create what type of bonds

Answer 6

induced mutation

covalent bonds which cause DNA damage and distortion

Question 7

intercalating agents like psoralen need _ for activation to form _ with neighboring pyrimidine residues

Answer 7

need UV light to form adducts

Question 8

UV light causes:

Answer 8

induced mutation; cause T-T dimers on adjacent base pairs

Question 9

ionizing radiation secondary effect which is:

Answer 9

induced mutation whose secondary effect cause free radicals and it is the free radicals that cause mutations

Question 10

what introduces mutations once a causative agent has acted upon DNA

Answer 10

subsequent DNA replications introduce mutations!

Question 11

which tautomers are favored?

Answer 11

amino, keto/amino, and keto

Question 12

what conformational isomer is favored?

Answer 12

anti

Question 13

when can nucleotides in DNA isomerize?

Answer 13

when DNA is single stranded ie during:

• replication
• transcription
• damage repair
• breathing

Question 14

what is it meant by “breathing”

Answer 14

motion; H bonds are temporary/noncovalent so double helix is constantly breathing = a lot of opportunity to make mutations (isomerize ability)

Question 15

what is a transition mispairing?

Answer 15

a purine to pyrimidine mismatch

Question 16

what is an example of a transition mispair

Answer 16

A -> C or G -> T

Question 17

what is the subsequent base that arises from transition in A or T that results in a mutation

Answer 17

A mispairs to C which makes G pair to that C

T mispairs to G which makes C pair to that G

Question 18

what is a transversion mispairing?

Answer 18

purine to purine or pyrimidine to pyrimidine mispair

Question 19

what mispair is more likely in a transversion and why?

Answer 19

purine to purine because pyrimidine to pyrimidine distorts

Question 20

why are transversions in general not popular?

Answer 20

need 2 things to go wrong simultaneously so chances are low

Question 21

what happens to helix diameter and rise in a transversion mispair

Answer 21

helix diameter is not altered significantly, the rise is a bit altered so the difference is in stacking and not length between sugars

Question 22

why didn’t mutation rate predictions not match up to observed rates?

Answer 22

there was a proof reading ability not taken into account (proof reading ability in bacteria)

Question 23

how was sdp discovered?

Answer 23

in short gene sequences with potential to form short stem-loop structures

Question 24

the sickle cell mutation is a transition of transversion mutation?

Answer 24

transversion

Question 25

only codon _ has a self-dupurinating site

Answer 25

codon 6 (guanine)

Question 26

changes in H bond potential arises from:

Answer 26

• unfavored isomers
• base analogs
• alkylating agents
• ionizing radiation

Question 27

structural roadblocks (hairpins, warping, covalent bonds) arises from:

Answer 27

• self-dupurination
• intercalators
• adducts
• UV light