dna replication 2

Question 1

how does type 2 topoisomerase work
(6 steps)

Answer 1

1. the topoisomerase recognises the supercoil and binds to it
2. atp binds to one of the a subunits
3. the backbone links to tyrosine on the subunit
4. the vertical section is passed through
5. joined back together and atp is consumed
6. caused a negative supercoil

Question 2

what is the overall process of topoisomerase

Answer 2

positive supercoil to negative

Question 3

how do type 2 topoisomerases affect the linking number

Answer 3

decrease by 2

Question 4

rank the speed of DNA forms running on the gel
fastest to slowest

Answer 4

1. supercoiled
2. linear
3. supercoiled

Question 5

what does bidirectional synthesis produce

Answer 5

theta replication

Question 6

what happens when cDNA molecules are replicated

Answer 6

catanenes form (two rings interlinked)

Question 7

how can we eliminate catanenes and how does it work

Answer 7

using topoisomerase 4
by cleaving passing through and resealing

Question 8

what is the solution to antiparallel strands

Answer 8

we loop back the 5’ to 3’ lagging end so it is on the correct side

Question 9

what does semi-discontinuous replication produce

Answer 9

2 nonidentical dsdna strand

Question 10

what will the lagging strand contain and why

Answer 10

nicks
as pol III cannot join them up as it replicates

Question 11

what are the fragments in the lagging strand called

Answer 11

Okazaki fragments

Question 12

how did they prove Okazaki fragments and why

Answer 12

the amount of small bp ssdna never decrease as they are continuously made

Question 13

what are the two processes that proves Okazaki fragments

Answer 13

1. pulse/ chase process
2. dna ligase mutants

Question 14

what joins the Okazaki frgaments together

Answer 14

dna ligase

Question 15

what is the composition of Okazaki fragments

Answer 15

rna primer and dna