In semiconservative DNA replication, what is the product of one round of DNA replication starting from a single double-stranded DNA molecule?

• A. One double-stranded DNA molecule composed entirely of newly synthesized strands
• B. One double-stranded DNA molecule in which both parental strands remain paired and the new strands form a separate duplex
• C. Two single-stranded DNA molecules, each composed entirely of parental strands
• D. Two double-stranded DNA molecules, each composed of one parental (old) strand and one newly synthesized strand

Answer: (D)

Verified step by step guidance

1. Understand the concept of semiconservative DNA replication: each original (parental) DNA strand serves as a template for the synthesis of a new complementary strand.
2. Recognize that the original double-stranded DNA molecule separates into two single strands during replication.
3. Each single parental strand pairs with a newly synthesized complementary strand, forming two double-stranded DNA molecules.
4. Note that each resulting double helix contains one parental (old) strand and one newly synthesized strand, preserving half of the original molecule in each product.
5. Conclude that after one round of semiconservative replication, the product is two double-stranded DNA molecules, each composed of one parental strand and one new strand.