Molecular genetics

Lore & Background

Molecular genetics arose from studies involving genetic transformation in bacteria. In 1944, Avery, MacLeod, and McCarty isolated DNA from a virulent strain of S. pneumoniae and converted a harmless strain to virulence, suggesting DNA is the genetic material. Chargaff's rules in 1951 showed base composition varies between species and that A=T and G=C. In 1953, Crick and Watson derived the 3-D double helix structure of DNA, building on X-ray crystallography by Franklin and Wilkins. The phage group, centered on Max Delbrück, contributed to understanding DNA replication, repair, recombination, and virus assembly; Yanofsky's work demonstrated co-linearity of gene and polypeptide.

Reader's Guide

Molecular genetics is significant for providing a powerful methodology to link mutations to genetic conditions, enabling the search for treatments of genetic diseases. The isolation of restriction enzymes in 1969 opened genetic engineering, leading to the first recombinant DNA molecule in 1971 and the first recombinant DNA organism in 1972. DNA sequencing techniques in the late 1970s and PCR in 1985 allowed scientists to conduct genetic screens relating genotypic sequences to phenotypes. The sequencing of the first whole genome (Haemophilus influenzae) and the human genome in 2001 culminated in genomics, which links molecular gene structure to protein or RNA function. Bioinformatics, using computer databases like NCBI and Ensembl, compares genes within and between species, linking mutations on an evolutionary scale.

Did You Know?

• Miescher discovered and isolated nuclein (DNA) from white blood cells in 1869.
• Chargaff's rules state that in natural DNA, adenine equals thymine and guanine equals cytosine.
• The first recombinant DNA organism was created by Cohen and Boyer in 1972 using bacterial transformation.
• The central dogma states DNA replicates, is transcribed into RNA, and RNA is translated into proteins.