Glossary I 323 



Gene frequency the number of loci at which a given allele is found 

 within a population, divided by the total number of loci at which it 

 could occur. 



Gene pool the total genetic information possessed by a population. 



Genetic assimilation the incorporation into the genotype, by a selective 

 process, of characteristics appearing in ontogeny as a response to the 

 environment. 



Genetic drift random fluctuation of gene frequency (usually due to 

 sampling error inherent in the genetic mechanism); present in all 

 populations, its effects are most evident in very small populations. 



Genetic homeostasis the tendency of populations under selection to 

 regress toward the original mean. 



Genetic load in a population, the average number of potential deaths 

 per individual due to genetic causes (lethals, semilethals, etc.). 



Genetic system all the factors, internal and external, that aflFect recom- 

 bination in an organism. 



Genetic variance that portion of the phenotvpic variance caused by 

 variation in the genetic environment of the individuals in a population. 



Genome the minimum set of nonhomologous chromosomes all of which 

 must be present to ensure the proper functioning of a cell. 



Genotype the totality of the genetic material of a cell (usually restricted 

 to nuclear genetic material); the total genetic endowment of an indi- 

 vidual; the genetic endowment of an individual at a given locus. 



Gens a subset of cuckoos tending to parasitize one kind of bird but not 

 necessarily geographically isolated from other such subsets. 



Golgi complex a cell organelle of unknown function found in most plant 

 and animal cells, often in proximity to the nucleus, and comprising a 

 series of concentricallv arranged cisternae without ribosomes, as seen 

 in electron micrographs. 



Grana pigment-containing structures within a plastid, usually appearing 

 as many disks stacked in series. 



Guanine one of the two purines (2-amino-6-hydroxypurine) involved 

 in the structure of DNA and RNA. 



Gynogenesis reproduction bv parthenogenesis in which stimulation by 

 a spermatozoan is necessary for the development of the egg. 



Haplodiploidy a genetic system found in some animals in which males de- 

 velop from unfertilized eggs and are haploid, the females being diploid. 



Haploid having the gametic number of chromosomes, or having a single 

 genome, in reproductive cells other than the gametes. 



Haplophase that part of the life cycle in which the gametic chromo- 

 some number is found in reproductive cells. 



Haplosis establishment of the gametic chromosome number, usually by 

 meiosis. 



Hardy-Weinberg law the law stating that, in a panmictic population, in 

 the absence of systematic pressures and genetic drift, the frequency of 

 autosomal genes at a given locus remains constant and that, after one 

 generation, the frequency of genotypes at the locus reaches equilibrium. 



