Nucleotide features in DNA-mRNA transcription

Steps:

• Locate labels in diagram: 1 marks base type on mRNA strand, 2 marks sugar molecule, 3 marks bonding between strands.
• Classify base at 1: mRNA uses pyrimidine (e.g., C) complementary to DNA purine (G).
• Identify sugar at 2: mRNA contains ribose, unlike DNA's deoxyribose.
• Determine bonds at 3: C-G pairing forms three hydrogen bonds.

Why D is correct:

• mRNA strand features pyrimidine bases (like cytosine) attached to ribose sugars, pairing with guanine via three hydrogen bonds per base-pairing rule.

Why the others are wrong:

• A: Incorrect sugar (deoxyribose is DNA-only) and base type mismatch.
• B: Wrong sugar (deoxyribose not in mRNA) despite correct bonds.
• C: Accurate on base and sugar but wrong bonds (C-G uses three, not two).

Final answer: D