Hemizygous; haplozygous
The condtion in which only one allele of a pair is present, as in sex linkage or as a result of deletion. Genes present only once in the genotype and not in pairs; as in haploids, in differential, segments of sex chromosomes, or in diploids as a result aeuploidy or loss of chromosome segments.

Heterokaryon
Cell with two or more different nuclei as a result of cell fusion. Opposite homokaryon.

Heterologous
From a different source, as in heterologous DNA.

Heterologous probe
A DNA probe that is derived from one species and used to screen for a similar DNA sequence from another species.

Hermaphrodite
1. Animal that has both male and female reproductive organs, or a mixture of male and female attributes. 2. A plant whose flowers contain both stamen and carpels.

Heteroalleles
Mutations that are functionally allelic but structurally non allelic; mutations at different sites in a gene.

HEPA filter
(high .efficiency particulate air filter) A filter capable of screening out particles larger than 0.3 mm. HEPA filters are used in 1. laminar air flow cabinets (hoods) for sterile transfer work. See prefilter.

Heterogametic sex
Producing unlike gametes with regard to the sex chromosomes. In mammals, the XY male is heterogametic, and the XY female is homogametic.

Heterogeneity
See genetic heterogeneity.

Heterogeneous nuclear RNA (hnRNA)
Large RNA molecules, which are unedited mRNA transcripts, or pre mRNAs found in the nucleous of a eukaryotic cell. See RNA.