A haploid sex cell, egg or sperm, that contains a single copy of each chromosome.

A genetically engineered microorganism.

A locus on a chromosome that encodes a specific protein or several related proteins. It is considered the functional unit of heredity. (See Dominant gene, Fusion gene, Gene amplification, Gene expression, Gene flow, Gene pool, Gene splicing, Gene translocation, Recessive gene, Regulatory gene.)

The presence of multiple genes. Amplification is one mechanism through which proto-oncogenes are activated in malignant cells.

The process of synthesizing multiple copies of a particular DNA sequence using a bacteria cell or another organism as a host. See DNA, Host.

The process of producing a protein from its DNA- and mRNA-coding sequences.

The exchange of genes between different but (usually) related populations.

The percentage of a given allele in a population of organisms. See Allele.

The addition of one or more copies of a normal gene into a defective chromosome.

The hereditary association of genes located on the same chromosome.

The chemical repair of a gene's defective DNA sequence. See DNA.

The totality of all alleles of all genes of all individuals in a particular population.

Combining genes from different organisms into one organism. See recombinant DNA.

The movement of a gene fragment from one chromosomal location to another, which often alters or abolishes expression.

Eventual extinction of a natural species as massive pollen flow occurs from another related species and the older crop becomes more like the new crop. See Gene flow.

The three-letter code that translates nucleic acid sequence into protein sequence. The relationships between the nucleotide base-pair triplets of a messenger RNA molecule and the 20 amino acids that are the building blocks of proteins. See Base pair, Nucleic acid, Nucleotide.

A disease that has its origin in changes to the genetic material, DNA. Usually refers to diseases that are inherited in a Mendelian fashion, although noninherited forms of cancer also result from DNA mutation.

Random variation in gene frequency from one generation to another.

The manipulation of an organism's genetic endowment by introducing or eliminating specific genes through modern molecular biology techniques. A broad definition of genetic engineering also includes selective breeding and other means of artificial selection.

A linear map of the relative positions of genes along a chromosome. Distances are established by linkage analysis, which determines the frequency at which two gene loci become separated during chromosomal recombination. (See Mapping.)

A gene or group of genes used to "mark" or track the action of microbes.

The genetic complement contained in the chromosomes of a given organism, usually the haploid chromosome state.

A library composed of fragments of genomic DNA. (See Library.)

The structure of DNA that determines the expression of a trait. See Phenotype.

A category including closely related species. Interbreeding between organisms within the same category can occur.

Genetically engineered organism.

Reproductive cell. See Somatic cell.

The repair or re- placement of a defective gene within the gamete-forming tissues, which produces a heritable change in an organism's genetic constitution.

Genetically modified organism.

Advances in genetics, petrochemicals, and machinery that culminated in a dramatic increase in crop productivity during the third quarter of the 20th century.

See Growth phase.

A serum protein that stimulates cell division when it binds to its cell-surface receptor.

The characteristic periods in the growth of a bacterial culture, as indicated by the shape of a graph of viable cell number versus time. (See Death phase, Lag phase, Logarithmic phase, Stationary phase.)