During semi-conservative DNA replication in bacteria, each daughter DNA molecule contains which of the following?

• A. Two newly synthesized strands
• B. Two original strands
• C. One original strand and one newly synthesized strand
• D. Two identical copies

Answer: (C)

In semi-conservative DNA replication, the two strands of the parent double helix separate and each serves as a template for a new complementary strand. DNA polymerase adds nucleotides to build the new strand in the 5' to 3' direction, using the old strand as a guide. The result is that each daughter DNA molecule has one original (parental) strand and one newly synthesized strand. This one-old-one-new arrangement is what distinguishes semi-conservative replication from other models. In bacteria, replication starts at the origin and proceeds in both directions, but the key outcome remains: every daughter molecule contains one old strand and one new strand.