DNA Mutations + Repairs (Chap 7 )

Question 1

altered phenotype

Answer 1

• gene mutated transcripted + translated

Question 2

Mutation def

Answer 2

• change in DNA base pair or chromo
• > somatic : affect only ind
• > germline: alters GAMETES and next generation

Question 3

Mutation rate

Answer 3

# of mut per cell division 
- ie # of mut per gene per generation

Question 4

Mutation frequency

Answer 4

• # of mut per total cells in defined pop

Question 5

Point Mutation types

Answer 5

(single base pair mutation )
-substitution:
-> Transition: change b/n pur-pyr and another pur-pyr
-> Transversion: change b/n pur-pyr and to pyr-pyr
-Insertion+delections:change in reading fraom mRNA downstram mutation=framshift
(truncation, elongation, jibberish)
-> missense : change norm codon to dif one=dif a.a.
-> nonsense : change codon to STOP = premature termination= truncated protein
-> neutral/silent : sim a.a is inserted= no change of protein function

Question 6

Reverse + Suppressor Mutation

Answer 6

• pt. Mut.
• > forward “ : change genotype from wt to mutant
• > backward”:change genotype from mutant to wt/true or partial wt

Question 7

Supressor mutation

Answer 7

• @ sites dif from orignal mut
• > mask or compensate for initial mut
  a) intragentic suppressor: @ same gene but dif site then orgi
  b) from dif gene=== supressor gene

Question 8

Spontaneous Mutation

Answer 8

(not induced by mutagen)

• during G1,S,G2 or movement of transposen
• repaired effectively and don’t stay in genome

Question 9

Deproination +Deamination

Answer 9

• loosing purine from DNA: breaking bond + deoxibose in backbone, common b/n sugar and purine, if not repaired before replication DNA polymerase will stall
  +
  -remouves amino group

= DNA lesions

Question 10

Induced Mutation

Answer 10

exposed to :
1.) physical
->radiation:
–> nonionizing : UVlight (dimer formations= buldge in DNA and disrupts replication)
–> ionizing: X-ray,cosmic ray, Radon(causes chromosom mut and death)
–> Dose and mutaion rate: linear and cummal effect ie radon gas
or
2.) chem mutations:
–> base analog: sim to normal base and readily absorbed ie transition mut of 5-Bromouracil
–> base modifying agent: hydroxylating (modifies OH- of C), Alkylating (add alkyl group to G), interclating (insert b/n bases of DNA= causes framshifts)

Question 11

Repair to DNA damage

Answer 11

• direct reversal: mismatch repair, photoreactivity, repair of allkylation
• excision repair “”: base excission, nucleotide, methyl-directed mismatch repair, translession dna synthesis and sos response

Question 12

environmental mutagens

Answer 12

• chem mutagens (frequent activity in liver)

- -> cause reversion mutations and increase grows w/out histones

Question 13

screening for toxins

Answer 13

Ames test: determine chem carcinogencity

–> auxtrophy - inability for org to make particular organic component required for growth

Question 14

mismatch repair

Answer 14

• DNA pol proofre and corrects
• e.coli : ‘ 3-5, exonucleus affirmed by mutator
• -> mutD gen encodes epsilon subunit of poly III

Question 15

photoreactivity ( light repair)

Answer 15

• repair UV induced pyrimidine dimer
• uv activates phltolylaseto solit dimers
• humans dont have photolylase

Question 16

alkylation damage ( methyl or ethyl groups)

Answer 16

• DNA enzyme can remove damage

- methyltransferase

Question 17

base excision repair

Answer 17

• glycolase recognize and remove damage
• base removed from sugar backbone
• -> produces gap where pol and ligase inserts base

Question 18

nucleotide excision repair

Answer 18

• 1. UvrA +B scan and fix damage
     
     2. UvrB +C cut it out
     3. UvrD unwind helix and release damaged
     4. ligase and DNA pol finish

Question 19

methyl-directed mismatch repair

Answer 19

• recognise +excise+repair
• > IDs nascent DNA(unmethyllated)

ie . E.Coli 1.mutS binds= complex w/ mutH and mutL

2. dna= contorts
3. mutH nicks dna+ excises exonucleous
4. dna pol+ ligase finish

Question 20

translesion DNA synthesis

Answer 20

(last reslrt mec)

• allow cell to survive when speckfic baseair cannot lccur
• SOS = lexA+ recA genes turn on ( facilitates dna pol translesion synth)
• -> dna damage = recA activated=> lexA tl self digest +lexA stops mediating dna repair