遗传学名词解释H.doc

文档介绍：HH substance -- The carbohydrate group present on the surface of red blood cells. When unmodified, it results in blood type O; when modified by the addition of harides, it results in type A, B, and AB. haploid --A cell anism having a single set of unpaired chromosomes. The gametic chromosome number. haplotype -- The set of alleles from closely linked loci carried by an individual and usually inherited asa unit. Hardy-Weinberg law -- The principle that both gene and genotype frequencies will remain in equilibrium in an infinitely large population in the absence of mutation, migration, selection, and nonrandom mating. heat shock --A transient response following exposure of cells anisms to elevated temperatures. The response involves activation ofa small number of loci, inactivation of some previously active loci, and selective translation of heat shock mRNA. Appears to be a nearly universal phenomenon observed anisms ranging from bacteria to humans. helicase -- An enzyme that participates in DNA replication by unwinding the double helix near the replication fork. helix-turn-helix motif -- The structure ofa region of DNA-binding proteins in which a turn of four amino acids holds two alpha helices at right angles to each other. hemizygous -- Conditions where a gene is present ina single dose in an otherwise diploid cell. Usually applied to genes on the X chromosome in heterogametic