Hypermedia Glossary Of Genetic Terms
|Heterozygote||The term coined by Bateson and Saunders (1902) for a zygote, or a diploid individual derived from it, which carries both members (Gk. heteros, different) of a pair of alleles. This might occur as a result of fusion of dissimilar gametes, or from mutation. Cf. heterozygosity|
|Zygote||Mostly diploid cell formed by union of twogametes or reproductive cells. Ovum (female gamete) fertilized by a sperm (male gamete).|
|Diploid||A full set of genetic material, consisting of paired chromosomes one chromosome from each parental set. Most animal cells except the gamete have a diploid set of chromosomes. The diploid human genome has 46 chromosomes. Compare haploid and polyploid.|
|Allele||The term coined by Bateson and Saunders (1902) for characters which are alternative to one another in Mendelian inheritance (Gk. Allelon, one another; morphe, form).
Now the term allele is used for two or more alternative forms of a gene resulting in different gene products and thus different phenotypes. In a haploid set of chromosomes there is only one allele at its specific locus. Diploid organisms have 2 alleles at a given locus, i.e. a normal and a mutant allele. A single allele for each gene locus is inherited separately from each parent (e.g., at a locus for eye colour the allele might result in blue or brown eyes). An organism is homozygous for a gene if the alleles are identical, and heterozygous if they are different.
|Gamete||Mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes (23 for humans).|
|Mutation||The term which De Vries introduced into biological literature for an abrupt change of genotype which is inherited. Any permanent and heritable change in DNA sequence. Types of mutations include point mutations, deletions, insertions, and changes in number and structure of chromosomes. (Cf. polymorphism)|
|Heterozygosity||The presence of different alleles of a gene at one or more loci. Cf. heterozygote|
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