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

• A. One double-stranded DNA molecule containing both original parental strands plus an additional newly synthesized copy
• B. Two double-stranded DNA molecules, each containing one parental (old) strand and one newly synthesized strand
• C. Two double-stranded DNA molecules, one composed entirely of parental strands and the other composed entirely of newly synthesized strands
• D. Two double-stranded DNA molecules, each containing two newly synthesized strands

Answer: (B)

Verified step by step guidance

1. Understand the concept of semiconservative DNA replication: each original DNA strand serves as a template for a new complementary strand, resulting in daughter DNA molecules that each contain one old (parental) strand and one new strand.
2. Start with one double-stranded DNA molecule, which consists of two complementary parental strands.
3. During replication, the two parental strands separate, and each acts as a template for synthesizing a new complementary strand.
4. After one round of replication, two double-stranded DNA molecules are formed, each composed of one parental strand and one newly synthesized strand.
5. Recognize that this outcome is distinct from conservative replication (which would produce one molecule with both parental strands and one with both new strands) and dispersive replication (which would produce strands with mixed old and new segments).