| assortative mating | Selection of a mate with preference for (or aversion to) a particular genotype, i.e., nonrandom mating. Synonym: nonrandom mating. (05 Mar 2000) |
|---|---|
| random mating | Totally haphazard mating with no regard to the genetic makeup (genotype) of the mate so that any sperm has an equal chance of fertilizing any egg. This rarely, if ever, occurs but the concept is impoortant in population genetics. Also called panmixus. (12 Dec 1998) |
| random mating equilibrium | <genetics> In a population containing the genotypes of AA, aa, and Aa, the frequency of AA will be p2, the frequency of aa will be q2, and the frequency of Aa will be 2 pq at equilibrium, where p is the frequency of A and q is the frequency of a. By the Hardy-Weinberg law, a ramdonly-mating population will eventually reach these frequencies and be at this equilibrium as long as there are no selection pressures on the population. (09 Oct 1997) |
| mating | The pairing of male and female for the purpose of reproduction. (05 Mar 2000) |
| mating isolate | A population separated from its neighbors by any means so that all or most matings occur within the population group. (05 Mar 2000) |
| mating type gene | Genes that, in Saccharomyces cerevisiae specify into which of the two mating types (a and _) a particular cell falls. Only unlike mating type haploids will fuse. The interest derives from the way in which mating type is switched, the existing gene is removed and a new gene, derived from a (silent) master copy elsewhere in the genome is spliced in. Later this gene will in its turn be replaced by a new copy of the old gene, also derived from a silent master. The a and _ genes code for pheromones that affect cells of the opposite mating type. Similar mating type genes are known from other yeasts and the switching mechanism (cassette mechanism) may be used more generally. (18 Nov 1997) |
| nonrandom mating | Selection of a mate with preference for (or aversion to) a particular genotype, i.e., nonrandom mating. Synonym: nonrandom mating. (05 Mar 2000) |
| ABO blood group | <haematology> The major human blood type system which describes the oligosaccharide glycoprotein antigens found on the surface of human blood cells. According to the type of antigen present, a person may be assigned a blood type of A, B, AB or O. A second type of antigen, the Rh factor, renders a positive or negative blood type. The ABO blood group system is important because it determines who can donate blood to or accept blood from whom. Type A or AB blood will cause an immune reaction in people with type B blood and type B and AB blood will cause a reaction in people with type A blood. Conversely, type O blood has no A or B antigens, so people with type O blood are universal donors. And since AB blood already produces both antigens, people who are type AB can accept any of the other blood types without suffering an immune reaction. (04 Jul 1999) |
| actinobacteria group | A group of gram-positive, heterogeneous bacteria. This group encompasses a range of morphologically, physiologically, and chemically different organisms and includes bacteria that form cocci, short rods, irregular rods, and mycelia that fragment. (12 Dec 1998) |
| alkyl group | <chemistry> A funtional group on an organic molecule which is derived from an alkane which has lost a hydrogen atom. (13 Nov 1997) |
| aluminum group | Aluminum, boron, gallium, indium, and thallium. (05 Mar 2000) |
| amino group | <biochemistry> An -NH2 group. Organic compounds which have this group are called amines. (09 Oct 1997) |
| anterior group of axillary lymph nodes | Lymph nodes located along the lateral thoracic vein; they receive the drainage of the pectoral region, including most of the drainage of the breast. Synonym: nodi lymphatici axillaris pectorales, anterior group of axillary lymph nodes. (05 Mar 2000) |
| apical group of axillary lymph nodes | The group of lymph node's located at the apex of the axillary fossa that receive lymphatic drainage from other groups of axillary node's and then drain in turn into the subclavian lymphatic trunk. Synonym: nodi lymphatici axillares apicales. (05 Mar 2000) |
| Bethesda-Ballerup Group | A group of citrate-utilizing, slow lactose-fermenting bacteria (family Enterobacteriaceae) which share a similar series of antigens with the lactose-fermenting citrobacters; these organisms are now included in the genus Citrobacter without a distinction between prompt and slow lactose fermentation. (05 Mar 2000) |