At the start of DNA replication, the double helix unwinds and the strands separate as shown in the diagram - Scottish Highers Biology - Question 1 - 2023
Question 1
At the start of DNA replication, the double helix unwinds and the strands separate as shown in the diagram.
(a) Name the enzyme that adds DNA nucleotides to newly s... show full transcript
Worked Solution & Example Answer:At the start of DNA replication, the double helix unwinds and the strands separate as shown in the diagram - Scottish Highers Biology - Question 1 - 2023
Step 1
a) Name the enzyme that adds DNA nucleotides to newly synthesised strands.
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Answer
The enzyme that adds DNA nucleotides to newly synthesised strands is DNA polymerase.
Step 2
b) Use information from the diagram to support this statement.
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Answer
Strand A is referred to as the lagging strand because it is synthesized in fragments, which are known as Okazaki fragments. The direction of synthesis moves away from the replication fork.
Step 3
c)(i) Give a reason why two different primers are used.
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Two different primers are used to ensure that both strands of DNA are replicated. One primer is required for each strand, allowing for efficient binding and amplification of both strands during PCR.
Step 4
c)(ii) State a temperature at which primers bind to the target sequence of DNA.
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The primers typically bind to the target sequence of DNA at a temperature ranging from 50°C to 65°C.
Step 5
d) Calculate how many copies of the DNA there would be after 9 minutes.
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One complete cycle of PCR takes 3 minutes, so in 9 minutes, there are 3 cycles. The number of copies doubles each cycle:
Starting with 30 molecules, after 3 cycles:
30imes23=30imes8=240
Therefore, there would be 240 copies of the DNA.
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