unit 1 KA2 - replication of DNA

Question 1

what is required to start DNA replication

Answer 1

DNA polymerase

Question 2

when is DNA replicated and what does it

Answer 2

prior to cell division, DNA polymerase

Question 3

what does DNA polymerase require to start replication

Answer 3

primers

Question 4

what are primers

Answer 4

a primer is a short strand of nucleotides which binds to the 3’ prime end of the template DNA strand allowing polymerase to add DNA nucleotides

Question 5

what enzyme is used to join fragments of DNA together

Answer 5

ligase

Question 6

describe the steps to DNA replication

Answer 6

• prior to cell division, DNA is replicated by a DNA polymerase
• DNA polymerase needs primers to start replication
• a primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing polymerase to add DNA nucleotides
• DNA is unwound and hydrogen bonds between bases are broken to form two template strands. DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand replicated in fragments

Question 7

what direction does DNA polymerase add DNA nucleotides onto the leading strand

Answer 7

5’ to 3’

Question 8

what does DNA polymerase use to add nucleotides to the strands

Answer 8

complementary base pairing

Question 9

what is the polymerase chain reaction

Answer 9

a process which amplifies DNA using complementary primers for specific target sequences

Question 10

what are primers in PCR

Answer 10

short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified

Question 11

what are the repeated cycles of heating and cooling in PCR. name the temperate and what happens at each stage

Answer 11

• 1) DNA heated to between 92-98 degrees to separate the strands.
• 2) it is then cooled to between 50 and 65 degrees to allow primers to bind to the target sequences
• 3) it is then heated to between 70 an 80 degrees for heat-tolerant DNA polymerase to replicate the region of DNA

Question 12

what are the practical applications of PCR

Answer 12

• solve crimes
• settle paternity suits
• diagnose genetic disorders

Question 13

what does PCR stand for

Answer 13

polymerase chain reaction