Glossary

Genetics glossary

914 definitions · page 8 of 16.

fate map: A map of an embryo showing areas that are destined to develop into specific adult tissues and organs. A map of the developmental fate of a zygote or early embryo showing the adult organs that will develop from material at a given position on the zygote or…
fecundity selection: The forces acting to cause one genotype to be more fertile than another genotype.
feedback inhibition: A post-translational control mechanism in which the end product of a biochemical pathway inhibits the activity of the first enzyme of this pathway.
fertility factor (F factor): The plasmid that allows a prokaryote to conjugate with and pass DNA into an F- cell. A bacterial episome whose presence confers donor ability (maleness).
Filial generation: Offspring generation. F1 is the first offspring or filial generation; F2 is the second; and so on. Successive generations of progeny in a controlled series of crosses, starting with two specific parents (the P generation) and selfing or intercrossing the…
filter enrichment: A technique for recovering auxotrophic mutants in filamentous fungi (in which non-auxotrophic organisms are filtered off leaving a residue of non-growing auxotrophs).
fingerprint: 1. The characteristic spot pattern produced by electrophoresis of the polypeptide fragments obtained through denaturation of a particular protein with a proteolytic enzyme. 2. See DNA fingerprint.
first division segregation (FDS): The allele arrangement (4+4) of spores within an ordered ascus that indicates the lack of recombination between a locus and its centromere. A linear pattern (4+4) of spore phenotypes within an ordered ascus for a particular allele pair, produced when the…
fitness (W): The relative reproductive success of a genotype as measured by survival; fecundity or other life history parameters. See Darwinian fitness and natural selection.
fixed allele: An allele for which all members of the population under study are homozygous, so that no other alleles for this locus exist in the population.
fixed breakage point: According to the heteroduplex DNA recombination model, the point from which unwinding of the DNA double helices begins, as a prelude to formation of heteroduplex DNA.
fluctuation test: A test used in microbial genetics to establish the random nature of mutation, or to measure mutation rates. An experiment by Luria and Delbruck that compared the variance in number of mutations among small cultures with subsamples of a large culture to…
focus map: A fate map of areas of the Drosophila blastoderm destined to become specific adult structures, based on the frequencies of specific kinds of mosaics.
Fokker-Planck equation: An equation that describes diffusion processes. It is used by population geneticists to describe random genetic drift.
footprinting: A technique to determine the length of nucleic acid in contact with a protein. While in contact the free DNA is digested. The remaining DNA is then isolated and characterized.
formylmethionine(fmet): A specialized amino acid that is the very first one incorporated into the polypeptide chain in the synthesis of proteins in Prokaryotes.
forward mutation: A mutation that converts a wild-type allele to a mutant allele. See also reversion.
founder effect: Genetic drift observed in a population founded by a small non representative sample of a larger population.
fragile site: A chromosomal region that has a tendency to break.
fragile-X syndrome: The most common form of inherited mental retardation. Named for its association with an X chromosome with a tip that breaks or appears uncondensed. Inheritance involves imprinting.
frameshift: A mutation in which there is an addition or deletion of one, two or a small number (not a multiple of three) of nucleotides that causes the codon reading frame to shift to one of two others from the point of the mutation during translation. Consequently the…
frameshift mutation: The insertion or deletion of a nucleotide pair or pairs, causing a disruption of the translational reading frame.
frequency histogram: A step curve in which the frequencies of various arbitrarily bounded classes are graphed.
frequency-dependent fitness: fitness differences whose intensity changes with changes in the relative frequency of genotypes in the population.
frequency-dependent selection: Selection that involves frequency-dependent fitness. Selection of a genotype depending on its frequency in the population.
frequency-independent selection: Selection in which the fitnesses of genotypes are independent of their relative frequency in the population.
frequency-interdependent fitness: fitness that is not dependent upon interactions with other individuals of the same species.
fruiting body: In fungi, the organ in which meiosis occurs and sexual spores are produced.
functional alleles: Mutants that fail to complement each other in a cis-trans complementation test.
fundamental number: The number of chromosome arms in a somatic cell of a particular species.
g-banding: Technique for producing banding patterns in eukaryotic chromosomes. Bands are produced by staining with Giemsa stain after pretreating chromosomes with trypsin. Each homologous chromosome pair has a unique pattern of g-bands, enabling recognition of…
gain-of-function dominant: A mutation in which dominance is caused by changing the specificity or expression pattern of a gene or gene product, rather than simply by reducing or eliminating the normal activity of that gene or gene product.
gamete: A germ cell having a haploid chromosome complement. Gametes from parents of opposite sexes fuse to form zygotes. A specialized haploid cell that fuses with a gamete from the opposite sex or mating type to form a diploid zygote; in mammals, an egg or a sperm.
gametic selection: The forces acting to cause differential reproductive success of one allele over another in a heterozygote.
gastrulation: The process of movements and infoldings of embryonic cells destined to become endoderm in early animal embryos, immediately following blastula (or blastoderm) stage, generating the blastopore.
gene: segregating and heritable determinant of the phenotype. The fundamental physical and functional unit of heredity, which carries information from one generation to the next. A segment of DNA, composed of a transcribed region and regulatory sequences that make…
gene amplification: A process by which the cell increases the number of a particular gene within the genome. The process by which the number of copies of a chromosomal segment is increased in a cell.
gene cloning: The production of a lineage of cells all of which contain one kind of DNA fragment of interest derived from a population of many kinds of DNA fragments. Operationally by: inserting (recombining) a population of DNA molecules, known to contain the DNA of…
gene conversion: A meiotic process of directed change in which one allele directs the conversion of a partner allele to its own form. In asci of Ascomycete fungi a 4:4 ratio of alleles is expected after meiosis, yet 6:2 and 5:3 ratios are sometimes observed. A model of…
gene dose: The number of copies of a particular gene present in the genome.
gene family: A set of genes in one genome all descended from the same ancestral gene. A group of genes that has arisen by duplication of an ancestral gene. The genes in the family may or may not have diverged from each other.
gene flow: The movement of genes from one population to another by way of interbreeding of individuals in the two populations.
gene fusion: The accidental joining of DNA of two genes, such as can occur in a translocation or inversion. Gene fusions can give rise to hybrid proteins or to the misregulation of the transcription of one gene by the cis regulatory elements (enhancers) of another.
gene interaction: The collaboration of several different genes in the production of one phenotypic character (or related group of characters).
gene locus: The specific place on a chromosome where a gene is located.
gene map: 1. A linear designation of mutant sites within a gene, based upon the various frequencies of interallelic (intragenic) recombination. 2. The DNA sequence of a gene annotated with sites of regulatory elements, introns, exons and mutations.
gene mutation: Mutation (point or larger change) that results from changes within the structure of a gene.
gene pair: The two copies of a particular gene present in a diploid cell (one in each chromosome set).
gene pool: All of the alleles available among the reproductive members of a population from which gametes can be drawn.
gene therapy: The correction of a genetic deficiency in a cell by the addition of new DNA and its insertion into the genome.
generalized transduction: The ability of certain phages to transduce any gene in the bacterial chromosome. Form of transduction in which any region of the host genome can be transduced. See specialized transduction.
genetic code: linear sequences of three nucleotides (triplets) that specify amino acids or termination (nonsense) codons during the process of translation at the ribosome. The correspondence between nucleotide triplets in DNA and amino acids in protein.
genetic dissection: The use of mutation and recombination to piece together the various components of a given biological function.
genetic engineering: Popular term for recombinant DNA technology.
genetic fine structure: The structure of the gene analyzed at the level of the smallest units of recombination and mutation (nucleotides).
genetic load: The relative decrease in the mean fitness of a population due to the presence of genotypes that have less than the highest fitness
genetic map: A linear designation of sites within a chromosome or genome, based upon the various frequencies of recombination between genetic markers. See linkage map
genetic marker: allele, DNA marker or cytogenetic marker used as experimental probe to keep track of an individual, a tissue, a cell, a nucleus, a chromosome, or a gene.
genetic polymorphism: The occurrence together in the same population of more than one allele or genetic marker at the same locus with the least frequent allele or marker occurring more frequently than can be accounted for by mutation alone.
genetic variance: Phenotypic variance resulting from the presence of different genotypes in the population.