A situation in which the total level of a gene product (a particular protein) produced by the cell is about half of the normal level and that is not sufficient to permit the cell to function normally. Another way to define haploinsufficiency is as a condition that arises when the normal phenotype requires the protein product of both alleles, and reduction of 50% of gene function results in an abnormal phenotype.
Haploinsufficiency can be due to a number of problems. One of the two copies of the gene may be missing due to a deletion. A mutation (change) in the gene may have wiped out production of message. Or the message or the protein produced by the cell may be unstable or degraded by the cell.
The term “haploinsufficiency” is of recent vintage. It was cobbled together for use in genetics, cell biology, and molecular medicine from “haploid” (one instead of two chromosomes or two genes) + “insufficiency.” Haploinsufficiency is related to hemizygosity.
- Hard measles
An acute highly contagious viral disease with fever, runny nose, cough, red eyes, and a spreading skin rash. The eight-day measles is the ordinary measles, also known as rubeola, a potentially disastrous disease. Measles may be complicated by ear infections, pneumonia, encephalitis (that can cause convulsions, mental retardation. and even death), the sudden onset of […]
- Hard palate
The first section of the bony part of the roof of the mouth, located in front of the soft palate.
- Hardy, James D.
the first human lung transplant in 1963, the first animal-to-human heart transplant in 1964, and a double-lung transplant that left the heart in place, in 1987. The 1964 transplant of a chimpanzee heart was done three years before the first human-heart transplant (by Christiaan Barnard). Dr. Hardy died in 2003 at the age of 84. […]
- Hardy-Weinberg law
A basic concept in population genetics that relates the gene frequency to the genotype frequency. The Hardy-Weinberg law can be used, for example, to determine allele frequency and heterozygote frequency when the incidence of a genetic disorder is known.
- Hashimoto disease
A progressive disease of the thyroid gland characterized by the presence of antibodies directed against the thyroid and by infiltration of the thyroid gland by lymphocytes (white blood cells activated by the immune system). Hashimoto disease is the most common cause of hypothyroidism in North America and Europe. In Hashimoto disease, the thyroid gland is […]