Question 17 of 25intermediate💡 UnderstandShort Answer2 marks

Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.

Correct Answer

The property of complementary base pairing between the two strands of DNA double helix led Watson and Crick to hypothesise the semi-conservative mode of DNA replication.

Due to this specific pairing, the two strands are complementary to each other, meaning if the sequence of bases in one strand is known, the sequence in the other strand can be predicted. This property suggests that the two strands can separate, and each strand can act as a template for the synthesis of a new complementary strand.

After the completion of replication, each DNA molecule would have one parental strand and one newly synthesised strand. This scheme was termed as semi-conservative DNA replication.

Exercise: EXERCISES | Q: 5 | (Page 31)
For More Understanding

Explanation

This answer is based on Watson and Crick's original 1953 statement where they noted that 'the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.' The textbook explains that base pairing confers a unique property - the strands are complementary to each other, enabling each strand to serve as a template for synthesizing identical daughter DNA molecules.

Solution Steps

  1. Step 1: Identify the property - complementary base pairing/specific pairing between strands

  2. Step 2: Explain how this property allows strands to separate and act as templates

  3. Step 3: Conclude with the result - one parental + one new strand = semi-conservative replication

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