Hybrid selection
The process of choosing individuals possessing desired characteristics from among a hybrid population.

Hybrid vigour; heterosis
The extent to which the performance of a hybrid in one or more traits is better than the average performance of the two parental populations.

4. The reaction by which the pairing of complementary strands of nucleic acid occurs. DNA is usually double-stranded, and when the strands are separated they will rehybridize under the appropriate conditions. Hybrids can form between DNA-DNA, DNA-RNA or RNA-RNA. They can form between a short strand and a long strand containing a region complementary to the short one. Imperfect hybrids can also form, but the more imperfect they are, the less stable they will be (and the less likely to form). To "anneal" two strands is the same as to "hybridize" them.

Hypervariable region
The parts of both the heavy and light chains of an antibody molecule that enable it to bind to a specific site on an antigen.

Hypervariable segment
A region of a protein that varies considerably between strains or individuals.

Hypocotyl
(Gr. hypo, under + kotyledon, a cup-shape hollow) Portion of an embryo or seedling below the cotyledons, which is a transitional area between stem and root.

Hyperploid
A genetic condition in which a chromosome or a segment of a chromosome is over represented in the genotype. Opposite: hypoploid.

Hypersensitive sites
Regions in the DNA that are highly susceptible to digestion with endonucleases.

Hypertonic
A solution with an osmotic potential greater than that of living cells, leading to water loss from, shrinkage or Plasmolysis of cells in a hypertonic situation. Opposite: hypotonic.