Chapter 21, Problem 1RQ

Why is DNA replication called “semiconservative”?

Summary Introduction

To explain: The reason why DNA replication is called “semiconservative”.

Introduction: Deoxyribonucleic acid (DNA) is the genetic material of prokaryotes, archaea, eukaryotes, and some viruses. Replication of DNA results in two copies of DNA that are split into two cells at the end of cell division. Replication is the starting mechanism in the central dogma.

Explanation of Solution

There are three proposed models of DNA replication:

• • Conservative model
• • Semiconservative model
• • Dispersive model.

Semiconservative model is the widely accepted and experimentally proved model. According to this model, each copy of the DNA replicated contains a parent strand.

Meselson–Stahl experiment supported the Watson and Crick model of DNA and provided evidences for semiconservative model of DNA replication.

In semiconservative replication, the two strands of parental DNA are used as a template each and a new strand is synthesized with enzymes and nucleotides. Thus, each daughter strand has a parental strand and a newly synthesized strand. Since a parental strand is conserved in daughter DNA, it is called semiconservative DNA replication.