Choose the best definition of how DNA replicates.
Each strand of a parent DNA molecule serves as the template for an identical strand in a daughter molecule; the parental and daughter strands bond after replication.
Each strand of a parent DNA molecule serves as the template for a complementary strand in a daughter molecule; the parental and daughter strand bond after replication.
Each strand of a parent DNA molecule serves as the template for a complementary strand in a daughter molecule; the parental strands rebond after replication.
The Correct Answer and Explanation is:
The best definition of how DNA replicates is:
“Each strand of a parent DNA molecule serves as the template for a complementary strand in a daughter molecule; the parental and daughter strands bond after replication.”
Explanation:
DNA replication is a crucial process by which a cell makes an identical copy of its DNA before cell division. The process ensures that each new cell receives an accurate copy of the genetic material. The key principle behind DNA replication is that the two strands of the parent DNA molecule separate, and each strand serves as a template for the creation of a new complementary strand.
Step 1: Unwinding of the DNA
The process begins with the unwinding of the double helix structure of the parent DNA molecule. This is achieved by an enzyme called helicase, which breaks the hydrogen bonds between the complementary base pairs (adenine with thymine, and cytosine with guanine), resulting in two single strands of DNA.
Step 2: Complementary base pairing
Each of the separated parent DNA strands serves as a template for the synthesis of a new complementary strand. The enzyme DNA polymerase adds the correct nucleotides (adenine, thymine, cytosine, and guanine) to the new strand by following the principle of complementary base pairing: adenine pairs with thymine, and cytosine pairs with guanine. This ensures that the daughter strand is complementary to the parent strand.
Step 3: Formation of two identical DNA molecules
Once the complementary strands are formed, the result is two double-stranded DNA molecules. Each of these molecules consists of one parent strand and one newly synthesized daughter strand. After replication, the newly formed daughter strands bond with their complementary parent strands to form the double helix structure again.
This process is known as semi-conservative replication, as each new DNA molecule contains one original (parental) strand and one newly synthesized (daughter) strand.
The other options in the question do not accurately describe the process. The parental and daughter strands do not “re-bond” as suggested in some choices; instead, the complementary bases pair together, forming two distinct double helices.