lec 21 DNA and RNA structure cont.

Question 1

what is it called when DNA is compacted or condensed?

Answer 1

supercoiling

Question 2

which enzyme helps condense DNA?

Answer 2

topoisomerase

Question 3

DNA with different coiled forms but the same nucleotide sequence are called?

Answer 3

topoisomers

Question 4

shape of DNA can be defined based on…

Answer 4

linkage number (LK)

Question 5

what is the formula for LK?

Answer 5

LK = Tw + Wr

Tw = # bp/10.5
Wr = number of overlaps in helix

Question 6

does supercoiled DNA travel faster in gel than relaxed DNA?

Answer 6

yes because it is smaller and has less resistance

Question 7

is DNA naturally positively charged?

Answer 7

No

Question 8

what amounts of agarose gel does a large DNA and small DNA want?

Answer 8

large wants small amounts of agarose (around 2%),
small wants large amounts of agarose (around 6%)

Question 9

what is the difference between type I topoisomerase and type II topoisomerase?

Answer 9

type I = nicks one strand of DNA to relax supercoil
type II = nicks two strands of DNA to relax supercoil, if ATP is introduced it can also introduce more supercoils

Question 10

what is the shape of topoisomerase?

Answer 10

it is shaped like a donut so DNA can enter the center