GENOTYPE

The term "genotype" refers to the specific genetic makeup of an individual and is often used with reference to allelic or mutant differences between individuals at one or more genes. The genotype of an individual is the genetic information within an individual's specific DNA sequence that sets the limits upon which nongenetic parameters like environment modulate normal and abnormal phenotypes. Geno-types at specific genes known to cause birth defects are used as diagnostics in genetic counseling to identify parents carrying specific disease genes and in prenatal genetic testing for offspring that will have birth defects. For example, a description of a mutation within the gene that causes cystic fibrosis is a geno-type, while manifestation of the disease is the pheno-type. The results of the Human Genome Project are being used to identify DNA sequences that cause birth defects. The genotypes associated with birth defects are then available for development of more accurate diagnostic tests.

See also:GENETIC COUNSELING; HUMAN GENOME PROJECT

Bibliography

Oak Ridge National Laboratory. "The Science behind the Human Genome Project." Available from http://www.ornl.gov/hgmis/project/info.html; INTERNET

David W.Threadgill

Robert E.Boykin

gen·o·type / ˈjenəˌtīp; ˈjē-/ • n. Biol. the genetic constitution of an individual organism. Often contrasted with phenotype.• v. [tr.] investigate the genetic constitution of (an individual organism): the person appointed will be responsible for maintaining and genotyping many different lines of zebra fish. DERIVATIVES: gen·o·typ·ic / ˌjenəˈtipik; ˌjē-/ adj.

genotype The genetic constitution of an organism, as opposed to its physical appearance (phenotype). Usually this refers to the specific allelic composition of a particular gene or set of genes in each cell of an organism, but it may also refer to the entire genome.

genotype The total set of alleles possessed by an organism. (Alleles are genes, which may be different or identical, that occupy matching sites on each of a pair of chromosomes.) Expression of these is responsible for the phenotype of the individual, which can be modified by environmental pressures.

Alan W. Cuthbert

genotype The genetic constitution of an organism, as opposed to its physical appearance (phenotype). Usually this refers to the specific allelic composition of a particular gene or set of genes in each cell of an organism, but it may also refer to the entire genome.