NCEA Type Questions: DNA REPLICATION
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Part A:
1. Describe the function of DNA polymerase.
Model Answer: DNA Polymerase links the nucleotides by bonding the phosphate group of one nucleotide to the sugar molecule of the adjacent nucleotide, forming the side of a new DNA molecule.
2. Describe the significance that the 3′ and 5′ ends have in the process.
Model Answer: New nucleotide can only be added at the 3′ end, so each new half strand is synthesized in the 5′-3′ direction. At the 5’end, the strand is extended into separate parts(Okazaki fragments) which grow by addition at their 3’ends and are joined by DNA ligase. The new strand at the 3’end is the leading strand and that at the 5′ end is the lagging strand.
3. Discuss the ways in which complementary strands are formed.
Model Answer: Both (leading and lagging) strands are formed by DNA replication with new nucleotides being added according to the base pairing rule. Eg. Adenine with Thymine, and Guanine with Cytosine. The complementary on leading strand is formed by adding new separate nucleotides, where as the complementary strand on lagging strand is formed by adding Okazaki fragments in the opposite direction, because the new strand cannot be synthesized in the 5′ direction. DNA ligase is used to join the bases and DNA polymerase is also used to form both strands.
4. Explain why the process is necessary for the growth of living organisms.
Model Answer: The DNA replication process allows the genetic material to be copied exactly so cell growth and repair can take place. This division is constantly taking place so damaged cells can be replaced and the organism can grow. It is important in mitosis, cell division. The DNA replication process during Mitosis allows new cells to be formed, that have identical genetic material through semi-conservative replication.
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