DNA replication

Question 1

characteristic feature of DNA

Answer 1

If one strand runs in the 5′ – 3′ direction, the other runs in 3′ – 5′ direction and thus are antiparallel (they run in opposite direction). The 5′ end has the phosphate group and 3’end has the OH group.

2. The angle at which the two sugars protrude from the base pairs is about 120° , for the narrow angle and 240° for the wide angle. The narrow angle between the sugars generates a minor groove and the large angle on the other edge generates major groove.
3. Each base is 0.34 nm apart and a complete turn of the helix comprises 3.4 nm or 10 base pairs per turn in the predominant B form of DNA.
4. DNA helical structure has a diameter of 20 Å and a pitch of about 3 Å. X – ray crystal study of DNA takes a stack of about 10 bp to go completely around the helix (360°).

Question 2

isotopes used for proving semiconservative nature of DNA

Answer 2

N 14 and N15

Question 3

any DNA molecule have ability to replicate autonomously is called

Answer 3

replicon

Question 4

in genetics the origin is

Answer 4

the point in DNA where replication starts

Question 5

which property is not associated with DNA polymerase 1

Answer 5

5’ to 3’ endonuclease activity

Question 6

the replicative polymerase in E.coli is

Answer 6

DNA polymerase III

Question 7

the function of E.coli polymerase II in the cell is

Answer 7

replication restart at the stalled replication fork

Question 8

okazaki fragments are

Answer 8

composed of DNA (lagging strand) and RNA ( primer)

Question 9

okazaki fragments are used to elongate

Answer 9

the lagging strand away from replication fork

Question 10

approximately how many okazaki fragments are synthesized during one round of replication in E.coli genome

Answer 10

E.coli genome consist of about 4,600,000 base pairs and consist approximately 4000 genes so,
2500 to 5000 okazaki fragments