Question 30 of 32intermediate💡 UnderstandShort Answer2 marks

The two strands in DNA are not identical but are complementary. Explain.

Correct Answer

The structure of DNA consists of two nucleic acid chains wound about each other in a double strand helix. These strands are held together by hydrogen bonds between pairs of bases.

The two strands are complementary rather than identical because hydrogen bonds are formed between specific pairs of bases. Adenine forms hydrogen bonds with Thymine, whereas Cytosine forms hydrogen bonds with Guanine. This specific base pairing means the sequence of one strand determines the sequence of the other, making them complementary to each other.

Exercise: EXERCISES | Q: 10.23 | (Page 22)
For More Understanding

Explanation

The answer is derived from the section describing the secondary structure of nucleic acids. The text explicitly states that the two strands are complementary because hydrogen bonds form between specific pairs: Adenine with Thymine, and Cytosine with Guanine. This specific pairing rule is the reason the strands are not identical (same sequence) but complementary (matching sequence).

Solution Steps

  1. Step 1: Identify the structure of DNA as a double strand helix held by hydrogen bonds.

  2. Step 2: State the specific base pairing rules mentioned in the text (Adenine-Thymine and Cytosine-Guanine).

  3. Step 3: Conclude that specific pairing makes the strands complementary, not identical.

PreviousNext