Why is DNA replication called semiconservative?

Because each new double helix consists of one strand from the original molecule and one newly made strand, so half of the parental DNA is conserved in each daughter molecule.

What is the central dogma of molecular biology?

It is the principle that genetic information generally flows from DNA to RNA to protein; DNA is transcribed into RNA, which is then translated into the amino acid sequence of a protein.

Molecular Genetics

Molecular genetics explains heredity in terms of the structure of DNA, the way it is copied and repaired, how it changes through mutation and recombination, and how its sequence is read out into proteins.

Definition

Molecular genetics is the study of the structure, replication, alteration, and expression of DNA and the genes it encodes, linking the hereditary units of classical genetics to their physical and chemical basis.

Scope

This area covers the double-helical structure of DNA and the evidence that it is the genetic material, semiconservative replication and the repair systems that preserve sequence fidelity, the molecular nature of mutation and the recombination that reshuffles sequences, and the flow of information from gene to protein through transcription, the genetic code, and translation. It addresses the molecular machinery of the gene from a genetics standpoint; broader cell and biochemical mechanisms are the province of neighboring biological subfields.

Sub-topics

Core questions

What features of DNA's structure allow it to store and faithfully copy genetic information?
How is DNA replicated semiconservatively, and how are replication errors corrected?
How do mutations arise at the molecular level, and how does recombination rearrange sequences?
How is the information in a gene decoded into a specific protein?

Key theories

DNA double helix and base pairing: DNA is an antiparallel double helix in which adenine pairs with thymine and guanine with cytosine, so each strand specifies the other and the molecule can be copied by templating.
Semiconservative replication: Each daughter DNA molecule retains one parental strand and one newly synthesized strand, the mechanism implied by base pairing and confirmed experimentally.
The central dogma and the genetic code: Genetic information flows from DNA to RNA to protein, with successive nucleotide triplets specifying amino acids according to a near-universal, redundant code.

Mechanisms

DNA polymerases copy each template strand in the five-prime to three-prime direction with proofreading, mismatch and excision repair systems correct damage, mutations result from replication errors and chemical or radiation damage, and the sequence is expressed through RNA-polymerase transcription and ribosomal translation of codons into amino acids.

Clinical relevance

The molecular view of the gene underlies recombinant DNA technology, genetic diagnostics, and gene therapy, while an understanding of mutation and repair illuminates how cancers arise and why defects in repair pathways predispose to disease.

History

Avery's 1944 transforming-principle experiments and the 1952 Hershey-Chase experiment identified DNA as the genetic material, Watson and Crick's 1953 double-helix model revealed how it could store and copy information, and the subsequent cracking of the genetic code in the 1960s completed the molecular foundation of genetics.

Key figures

James Watson
Francis Crick
Rosalind Franklin
Matthew Meselson

Seminal works

watsonCrick1953
griffiths2020

Frequently asked questions

Why is DNA replication called semiconservative?: Because each new double helix consists of one strand from the original molecule and one newly made strand, so half of the parental DNA is conserved in each daughter molecule.
What is the central dogma of molecular biology?: It is the principle that genetic information generally flows from DNA to RNA to protein; DNA is transcribed into RNA, which is then translated into the amino acid sequence of a protein.