Heterologous protein
See recombinant protein

Heterotrophic
A group of organisms which obtain carbon for synthesis from other organic matter or proteins.

Histoglobulin
See histocompatibility complex.

Histology
(Gr. histos, cloth, tissue + logos, discourse) Science that deals with the microscopic structure of animal and plant tissues histone Group of water soluble proteins rich in basic amino acids, closely associated with DNA in plant and animal chromatin. Histones are involved in the coiling of DNA in chromosomes and in the regulation of gene activity.

Heterozogote
(adj: heterozygous) (Gr. heteros, different + zygon, yoke) An individual that has different alleles at the same locus in its two homologous chromosomes.

Hfr
High frequency recombination strain of Escherichia coli; in such strains, the F episome is integrated into the bacterial chromosome.

HGH
Human growth hormone, q.v.

Histocompatibility
The degree to which tissue from one organism will be tolerated  by the immune system of another organism.

Histocompatibility complex; histocompatibility system
The collection of genes coding for peptides present on the surface of nucleated cells; these peptides are responsible for the differences between genetically non identical individuals. These peptides were originally called histocompatibility antigens. They are now called histoglobulins, reflecting their structural similarity to immunoglobulins.

HIV
Human immunodeficiency virus.The retrovivrus that causes AIDS in humans.