Lecture 11

Question 1

What does EMS (ethyl methane sulphonate) do?

Answer 1

Stick to G’s

This damaged G (G*) resembles an A

Results in GC to AT bp substitution
(GC to GC, replicated to GT and GC) (result is AT mutation)

Question 2

What is the result of EMS?

Answer 2

GC to AT mutation

(G*C)

Question 3

What is EMS used for?

Answer 3

to cause mutations in model organisms

Question 4

What is the issue with benzo[a]pyrene?

Answer 4

causes mutations

a derivative of benzo[a]pyrene sticks to a G

if the damage isn’t repaired:

GC turns to TA

Question 5

What does the NHEJ (non-homologous end-joining) system do?

Answer 5

gamma rays and X rays break DNA

1) recognition of broken DNA ends
2) bring ends together
3) ligate ends together

Question 6

What is caused by NHEJ?

Answer 6

chromosome rearrangements

when double stand breaks occur (such as by X or gamma rays), the NHEJ pathway repairs them, but if telomeres are lost or multiple breaks exist, NHEJ can misjoin DNA ends, leading to chromosome rearrangements

improper repair of dsDNA breaks by NHEJ can cause any type of chromosome rearrangement

Question 7

Why might inversions be harmless?

Answer 7

inversions don’t change the amount of DNA, but they can still cause trouble (such as recombinant problems in meiosis and unbalanced gametes)

Question 8

Improper repair of dsDNA breaks by NHEJ can cause any type of chromosome rearrangement. What do these rearrangements include?

Answer 8

deletion, duplication, inversion, translocation

Question 9

How is a human male chromosome with an inversion named?

Answer 9

46,XY,inv(9),(band)

such as

46,XY,inv(9),(p12q13)

Question 10

What happens to lacRep+ when given EMS?

Answer 10

lacRep-