Dictionary

heterosexual 1 A person who is sexually attracted to persons of the opposite sex. Colloquially known as straight. 2 The act or habit of oppositesex attraction.

heteroploid A different chromosome number than the normal number of chromosomes. Abnormal numbers of chromosomes are associated with a number of disorders. For example, Down syndrome is the result of having three instead of two chromosome 21s.

heteromorphism Something that is different in form. Chromosome heteromorphisms are normal variations in the appearance of chromosomes.

heterokaryon A cell with two separate nuclei formed by the experimental fusion of two genetically different cells. For example, heterokaryons composed of nuclei from Hurler syndrome and Hunter syndrome, both diseases of mucopolysaccharide metabolism, have normal mucopolysaccharide metabolism. This proves that the two syndromes affect different proteins and so can correct each other in the…

heterochromia iridis, sectoral A difference in color within an iris. A person with both brown and blue in the same eye has sectoral heterochromia iridis.

heterochromia iridis A difference in color between the iris of one eye and the iris of the other eye. A person with one brown eye and one blue eye has heterochromia iridis.

heterochromatin A genetically inactive part of the genome. Heterochromatin was so named because its chromosomal material (chromatin) stains more darkly throughout the cell cycle than most chromosomal material (euchromatin). There are two types of heterochromatin: constituitive heterochromatin and facultative heterochromatin.

hetero- Prefix meaning different, as in heteromorphism (something that is different in form) and heterozygous (possessing two different forms of a particular gene). The opposite of hetero- is homo-.

herpetiform virus A virus with the characteristic shape and behavior of a virus in the herpes family. Not all members of the herpes virus family have been identified. Some herpetiform viruses may eventually be called herpesviruses, and others are merely similar to herpesviruses. See also herpesvirus.

herpesvirus One of a family of viruses that contain DNA and that cause infections in humans (human herpesviruses) or animals. Herpesviruses are common and often live in the host’s tissue for years or even decades without causing symptoms.

herpes zoster The herpes virus that causes chickenpox (varicella). Herpes zoster and chickenpox are usually contracted in childhood, at which time the virus infects nerves (namely, the dorsal root ganglia). It remains latent for years but can later be reactivated to cause shingles (blisters over the distribution of the affected nerve). Shingles is often accompanied…

herpes simplex virus type 2 A herpes virus that causes genital herpes, which is characterized by sores in the genital area. Abbreviated HSV-2. HSV-2 may also be a cause of fever blisters around the mouth. In rare cases, as when a patient’s immune system is severely compromised, this virus can cause widespread infection of the…