4. Which one of the following statements is NOT correct?
(1) Together with proteins rRNA provides a site for polypeptide synthesis.
(2) All DNA molecules are unbranched polymers of nucleotides.
(3) DNA is synthesized in a 5′-3^’ direction while RNA synthesis occurs in a 3′- 5′ direction.
(4) A tRNA anticodon may pair with more than one codon.

 

MCQ: Which One of the Following Statements Is NOT Correct?

1. Together with proteins, rRNA provides a site for polypeptide synthesis.

2. All DNA molecules are unbranched polymers of nucleotides.

3. DNA is synthesized in a 5’→3’ direction, while RNA synthesis occurs in a 3’→5′ direction.

4. A tRNA anticodon may pair with more than one codon.

Correct Answer: (3) DNA is synthesized in a 5’→3’ direction while RNA synthesis occurs in a 3’→5′ direction

Explanation:

Let’s examine each option one by one to identify the incorrect statement.

Option 1: rRNA provides a site for polypeptide synthesis – TRUE

• Ribosomal RNA (rRNA), along with proteins, forms ribosomes — the site where translation occurs.

• It plays structural and catalytic roles in peptide bond formation.

Option 2: DNA molecules are unbranched nucleotide polymers – TRUE

• DNA is a linear (unbranched) polymer made of nucleotide monomers (deoxyribonucleotides).

• Double-stranded DNA forms a helical structure, but remains unbranched.

Option 3: DNA is synthesized 5’→3’, RNA synthesis 3’→5’ – NOT CORRECT

• Both DNA and RNA are synthesized in the 5’→3’ direction.

• RNA polymerase adds nucleotides to the 3’ OH end of the growing RNA strand.

• So, this statement is factually incorrect and is the right answer to this MCQ.

Option 4: tRNA anticodon may pair with more than one codon – TRUE

• This is due to the wobble hypothesis.

• The third base of the codon often allows non-standard pairing, enabling one tRNA to recognize multiple codons coding for the same amino acid.

Correct Answer Recap: (3)

RNA synthesis also occurs in the 5’→3’ direction, just like DNA — so the statement is NOT correct.

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