In semiconservative DNA replication, what is the composition of each daughter DNA double helix after replication is complete?

• A. Each daughter double helix contains two newly synthesized strands; the parental DNA is not retained.
• B. One daughter double helix is composed of two parental strands, and the other is composed of two newly synthesized strands.
• C. Each daughter double helix contains one parental (old) strand and one newly synthesized strand.
• D. Each parental strand remains intact, and new DNA is synthesized as a separate double helix that does not pair with the parental strands.

Answer: (C)

Verified step by step guidance

1. Understand the concept of semiconservative DNA replication: during this process, the double helix unwinds, and each original (parental) strand serves as a template for the synthesis of a new complementary strand.
2. Recognize that after replication, each daughter DNA molecule consists of one strand from the original parental DNA and one newly synthesized strand.
3. Recall that this mechanism ensures genetic continuity because each daughter molecule retains half of the original DNA molecule, preserving the sequence information.
4. Contrast semiconservative replication with other models such as conservative replication (where parental strands stay together) and dispersive replication (where parental and new DNA are interspersed in both strands).
5. Conclude that the correct composition of each daughter DNA double helix after semiconservative replication is one parental strand paired with one newly synthesized strand.