Dictionary

histone A protein around which DNA coils to form chromatin. Without histones, DNA could not organize into chromosomes.

Histoplasma capsulatum A fungus that is found worldwide that is particularly common in the central and eastern parts of the US. It is carried in bird and bat droppings, and it is deposited in the soil. Although people can contract histoplasma from their environment, it cannot be passed from person to person. While most persons…

histoplasmosis A disease caused by the fungus Histoplasma capsulatum. Most people with histoplasmosis have no symptoms. However, it can cause acute or chronic lung disease and progressive disseminated histoplasmosis, which affects a number of organs. Infants, young children, and older persons—particularly those with chronic lung disease—are at increased risk for severe disease. Disseminated histoplasmosis is…

heterozygote An individual who has two different forms of a particular gene, one inherited from each parent. A heterozygote for cystic fibrosis (CF) has the CF gene on one chromosome 7 and the normal paired gene on the other chromosome 7. Also known as carrier.

heterozygous Possessing two different forms of a particular gene, one inherited from each parent.

HEV Hepatitis E virus. See hepatitis E.

hex-A deficiency Hexosaminidase A deficiency. See Tay-Sachs disease.

hexadactyly The presence of an extra digit: a sixth finger or toe. Hexadactyly is a very common birth defect. The sixth digit can be located in three different locations: on either side of the extremity or somewhere in between. With the hand, for example, the extra finger can be out beyond the little finger (ulnar…

hexoseaminidase A An enzyme whose deficiency causes Tay-Sachs disease. See also Tay-Sachs disease.

HGV Hepatitis G virus. See hepatitis G.

HHS The Department of Health and Human Services of the US government, which has jurisdiction over public health, welfare, and civil rights issues and is the highest-level US government body with such jurisdiction. Agencies under HHS include the Food and Drug Administration (FDA) and the National Institutes of Health (NIH).

HHV Human herpesvirus. HHV-1 is herpes simplex type 1. HHV-2 is herpes simplex type 2. HHV-3 is herpes zoster, the cause of shingles. HHV-4 is the Epstein-Barr virus, the cause of infectious mononucleosis. HHV-5 is cytomegalovirus. See also human herpesvirus 6; human herpesvirus 7; human herpesvirus 8.