Question

What does it mean when we say that DNA replication is semi-conservative?

A. New DNA molecules are composed of one strand of the old molecule and one new strand.
B. New DNA molecules are composed of two completely new strands.
C. New DNA molecules are composed of strands that are a mixture of sections from the old molecule and sections that are new.
D. New DNA molecules vary in makeup and can be made of some old and some new nucleotides.

Answer 1

DNA replication is semi-conservative because each new DNA molecule consists of one old (parental) strand and one newly synthesized strand.

Step-by-step explanation:

When we say that DNA replication is semi-conservative, we mean that each new DNA molecule is composed of one strand from the original molecule and one newly synthesized strand. Option A is correct: New DNA molecules are composed of one strand of the old molecule and one new strand. This is because during DNA replication, each of the two strands of the DNA double helix serves as a template from which new strands are copied. The result is that each new DNA molecule conserves half of the original DNA molecule, meaning one original strand pairs with one new counterpart in each new DNA molecule.