Genetics, Molecular Basis of
Published Online: 15 SEP 2006
Copyright © 2006 Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved.
Reviews in Cell Biology and Molecular Medicine
How to Cite
Snustad, D. P. 2006. Genetics, Molecular Basis of. Reviews in Cell Biology and Molecular Medicine. .
- Published Online: 15 SEP 2006
The phenotype of a living organism is controlled by its genotype, the summation of its genetic information, acting within the constraints imposed by the environment in which the organism exists. Much of the genetic material of an organism is organized into basic functional units called genes, which specify RNA and/or protein products. Some genes encode one primary gene product, either an RNA molecule or polypeptide. Other genes produce two or more related polypeptides by RNA editing, differential transcript splicing, or the assembly of genes from gene segments during development. The genetic information of all living organisms, whether viruses, bacteria, corn plants, or humans, is stored in the sequence of bases (purines and pyrimidines) or base pairs in the deoxyribonucleic acid (DNA) present in their chromosomes. In some viruses, the genetic information is stored in the sequence of bases in ribonucleic acid (RNA). The genetic information is encoded using a four-letter alphabet: the four bases adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, uracil (U) replaces the thymine present in DNA. In the double-stranded DNA present in most cellular organisms, adenine and thymine form one base pair (A:T) and guanine and cytosine form a second base pair (G:C).
The genetic material of an organism must carry out three essential functions: (1) the genotypic function, transmission of the genetic information from generation to generation; (2) the phenotypic function, directing the growth and development of the offspring into mature, reproductive adults; and (3) the evolutionary function, mutation, allowing organisms to evolve in response to changes in the environment. Mutation produces new genetic variability, which provides the raw material for evolution. Recombination of genetic material occurs by the independent assortment of nonhomologous chromosomes and by crossing-over between homologous chromosomes. This recombination provides new combinations of genes and thus new phenotypes on which natural selection acts during the process of evolution.
- Autosomal Inheritance;
- CentiMorgan (cM);
- Complementation Test;
- Frameshift Mutation;
- Gain-of-function Mutation;
- Genetic Map;
- Independent Assortment;
- Loss-of-function Mutation;
- Sex-linked Inheritance;
- Suppressor Mutation;
- Transposable Genetic Element;