Mutations and repair

Question 1

Polymorphisms occur in…while mutations occur in…

Answer 1

populations, individuals

Question 2

Spontaneous mutations include…

Answer 2

Depurination and Deamination

Question 3

Induced mutations include…

Answer 3

Radiation, Ionizing radiation, chemical mutagens, environmental mutagens

Question 4

Types of chemical mutagens…

Answer 4

Base analog(5-bromouracil), Base modifying agent, Intercalating agent(ehidium bromide)

Question 5

DNA repair 2 categories…

Answer 5

1) Direct reversal repair:
- Mismatch(DNA pol exonuclease)
- Uv-induced(Photolyase, phr gene)
- Alkylation(removing alkyl)
2) Excision repair:
- Base excision(glycosylase)
- Nucleotide excision
- Methyl-directed mismatch(also exonuclease)
- Translesion DNA synthesis(special DNA pol’s synthesized)

Question 6

Transposable elements..

Answer 6

Replicative transposition(copy-paste): gene copy in one and moves to another
Conservative transposition(cut-paste): gene excises and moves to another
Insertion sequence element: IS flanked by inverted repeats
Transposons:
- Composite: IR IS IR GENOME IR IS IR
- Noncomposite: IR GENOME IR

Transposase in IS and composite
Transposase and resolvase in noncomposite.

Question 7

Human retrotransposons

Answer 7

LINES:
- Encode their own transposase
- Autonomous element
- 1k-7k bp
- L1 causes hemophilia

SINES:
- Non-autonomous elements
- Depend on LINES for transposase
- 100-400 bp
- Alu family(Alu1) causes neurofibromatosis

Question 8

DNA repair mechanisms(2 main types)…

Answer 8

Single strand breaks:
- MMR: template strand is methylated. The new strand isn’t
- BER: Used for deaminated/depurination bases
- NER: Used for bulky adducts/crosslinks (Xeroderma)

Double strand breaks:
- Non-homologous end joining: In G1…re-seals any 2 broken strands
- Homologous recombination: G2/M and S…uses homologous strand as a template