(3.1.5.2) DNA replication

Question 1

describe the replication of DNA

Answer 1

• DNA helicase unwinds the double helix by breaking the hydrogen bonds
• both strands act as templates;
• free DNA nucleotides line up in complementary pairs (adenine-thymine and guanine-cytosine)
• DNA polymerase joins nucleotides on new strand, forming phosphodiester bonds in the sugar-phosphate backbone by catalysing condensation reactions
• each new DNA molecule consists of one old/original/template strand and one new strand;

Question 2

describe and explain how the structure of DNA allows accurate replication

Answer 2

• two strands therefore semi-conservative replication (possible);
• base pairing/ hydrogen bonds holds strands together
  *hydrogen bonds weak and can be easily broken, which allow strands to separate;
  *bases sequence exposed so can act as template and can be copied;

Question 3

what are the three models of DNA replication?

Answer 3

• semi-conservative (parental strand splits every time)
• conservative (one parental strand is unchanging)
• dispersive (little bits of parental strand being spread out)