Lecture 11- DNA Replication I

Question 1

Why is DNA replication important

Answer 1

Passing on genetic information during cell division and when organisms reproduce

Question 2

Mechanism of DNA replication

Answer 2

Semi conservative-each new molecule has one parent strand and one new daughter strand

Question 3

Meselson and Stahl experiment overview

Answer 3

Grow bacteria in heavy 15N- heavy DNA
Grow bacteria in normal 14N (one generation)- Hybrid DNA
Grow bacteria in normal 14 N - light DNA & hybrid DNA

Question 4

Each DNA strand has 5’ …. at one end and 3’ …. at the other end

Answer 4

Phosphate
Hydroxyl

Question 5

Bases can only add at the …. end

Answer 5

3’ hydroxyl

Question 6

Leading strand- made ….-primer extended by DNA ….. from …. to …. end

Answer 6

Continuously
Polymerase
5’
3’

Question 7

Lagging strand- made …. as can’t be made in the same direction DNA is unwound. Made in a series of ….

Answer 7

Discontinuously
Fragments

Question 8

How does DNA replication get started if a 3’ end is needed to prime DNA synthesis?

Answer 8

DNA replication is primed by RNA
RNA synthesis doesn’t need a primer
RNA synthesised by primase and Okazaki fragments formed

Question 9

Length of Okazaki fragment

Answer 9

1000-2000 bp in length

Question 10

RNA primers are removed by …. and Rnase H

Answer 10

DNA polymerase I

Question 11

….. exonuclease removes RNA

Answer 11

5’-3’

Question 12

DNA ….. glues together

Answer 12

Ligase

Question 13

….. closes the nicks in the DNA backbone between Okazaki fragments

Answer 13

DNA ligase

Question 14

Replication fork

Answer 14

The point where the double stranded DNA is unwound by the helices enzyme

Question 15

DNA replication initiates ….. So DNA replication can be

Answer 15

Somewhere in the double stranded region
Bidirectional or unidirectional

Question 16

Direction of fork movement can be determined using….

Answer 16

Radioisotopes and photographic emulsion