DNA Replication

Question 1

What is the role of DNA Helicase?

Answer 1

separates double helix into two strands
breaks H bonds between base pairs

Question 2

What is the role of free DNA nucleotides?

Answer 2

form H bonds with single strands
Adenine to Thymine
cytosine to Guanine

Question 3

What is the role of DNA Polymerase?

Answer 3

forms phosphodiester bonds between nucleotides to form new strand of DNA

Question 4

Why does DNA need to be replicated?

Answer 4

so that cell produced through mitosis has a complete set of chromosomes
23 pairs (diploid)

Question 5

What is the evidence for DNA synthesis?

Answer 5

Semi-conservative replication
Meselson and Stahl proved
used two isotopes of nitrogen - heavy (N 15) and light (N 14)

Question 6

What is semi conservative replication?

Answer 6

half of the strands in each new DNA molecule are from the original DNA molecules

Question 7

What was Meselson and Stahl’s investigation?

Answer 7

2 samples of bacteria grown, one heavy and one light
a sample of DNA taken from each then spun in centrifuge
DNA from heavy N sat lower then light N
Both bacteria sample grown in heavy put in light
were left for one round of replication then another sample centrifuged
DNA settled in middle
showed both isotopes mixed so bacteria had semi-conservatively replicated in light N

Question 8

What was the discovery?

Answer 8

semi-conservative replication is universal method of replication for all living things