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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Haploinsufficiency - Heavy Chain Disease
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Hammerhead ribozymes
small trans-cleaving ribozymes charaterised by a hammerhead motif containing three short helices flanking a central catalytic core of 15 conserved nucleotides.
Hanes-Wolf
A linear transformation of the Michaelis –Menten equation. It gives a straight line plot of [S]/V against [S]
Hanging droplet technique
See microdroplet array.
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Hank’s balanced salt solution A solution used in tissue culture medium that provides the required minerals, pH and osmotic environment.
Haploid Containing one copy of each autosome and one sex chromosome. The haploid state is usually seen in gametes (sperm and ovum)
Haploinsufficiency A condition in which the protein produced by a single copy of a normal gene is insufficient to ensure normal function.
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Haplotype
1. A group of closely linked alleles on a chromosome. 2. The pattern of restriction enzyme sites along a chromosome.
Hapten
A small molecule that is not itself immunogenic but becomes immunogenic after conjugation to a carrier protein or cells, and induces antibody, which can bind the hapten alone in the absence of carrier.
Haptoglobin
A plasma protein. An α – globulin that binds haemoglobin released during intravascular haemolysis.
Hardware
The physical components of a computer.
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Hartnup disease
A rare autosomal recessive disorder of tryptophan metabolism named after the first patient. There is a defect in the transport of tryptophan across the intestine and the renal tubules. The unabsorbed by the intestine and excreted in the urine. Due to excessive urinary loss of tryptophan, plasma levels are low and the formation of niacin from tryptophan is reduced. The molecular basis of the defect is suggested to be a mutation o shared neutral amino acid transport protein. Due to niacin deficiency, pellagra-like symptoms develop. Aminoaciduria occurs with increased excretion o neutral monoamino monocarboxylic acids. Hartnup disease can be diagnosed by the amino acid pattern in urine. Treatment involves intake of a high protein diet. Oral niacin is administered to alleviate pellagra like symptoms.
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Harvesting
1. The process involved in gathering ripened crops. 2. The collection of organs from donors for transplantation. 3. Collection of cells, organisms or growth medium from an experimental population. Harvesting is done for analysis and extraction of biochemicals.
Hashimoto’s disease
A hypothyroid state in which circulating antithyroid antibodies present in high concentrations cause progressive destruction of thyroid tissue.
HDL
See high-density lipoproteins.
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Hardly- Weinberg equilibrium
The frequencies of genotype at a locus that result from random mating at that locus. For two alleles, A1 and A2, with frequencies p and q respectively, the Hardy-Weinberg equilibrium frequencies are p2 A1A1, 2pqA1A2, q2A2A2. Most loci in most populations are in Hardy-Weinberg equilibrium. The Hardy-Weinberg law, which predicts frequencies of genotypes, is one of the great unifying themes of biology.
HAT (histone acetyltransferase)
An enzyme that modifies histones by addition of acetyl groups. Some transcriptional coactivators also have HAT activity.
HAT medium
A type of cell-culture growth medium containing hypoxanthine, aminopterin and thymidine used for negative selection of mutant cell incapable of utilizing hypoxanthine and/or thymidine to make nucleic acids. Aminopterin is an antifolate drug that inhibits Dihydrofolate reductase while hypoxanthine and thymidine are intermediates in DNA synthesis. HAT medium is used for the preparation of monoclonal antibodies.
Haworth perspective formula
A method for representing cyclic chemical structures in order to define the configuration of each substituents group. This method is commonly used for representing sugars.
Hay’s test
A test used to detect bile salts in urine. This is based on the fact that bile salts when present in urine, lower surface tension causing Sulphur particles layered on the urine sample to sink.
HBIOI
A substrain of the bacterium E.coli used as a cloning host due to its high efficiency of DNA uptake and transformation.
HCG
Human chorionic gonadotrophin. A hormone synthesized by the placenta following implantation of the uterus. Measurement of hCG in urine is used as a pregnancy test.
HCG stimulus test
A diagnostic test for hypogonadism. hCG which is similar in action to LH can be used to test Leydig cell function. Blood is taken at 9.00 h for testosterone estimation followed by intramuscular injection of 20000 IU hCG. On the third day, a second injection of hCG (2000 IU) is given. Blood is withdrawn on the fifth day for testosterone estimation. In normal persons, there is an increase in plasma testosterone to above the upper limit of the reference range. In primary testicular failure, the response is decreased or absent, whereas, a normal response may occur in secondary testicular failure.
HDAC (histone deacetyltransferase, histone deacetylase)
An enzyme that removes acetyl groups from histones. Deacetylation can cause repression of transcription.
HDL2
An intermediate formed during HDL metabolism.
HDL3
An intermediate formed during HDL metabolism.
HDLc (HDL1)
A lipoprotein found in the plasma of diet- included hypercholesterolaemic animals. It is rich in cholesterol and contains apoE.
Heat
A form of energy that is transferred from higher temperature to lower temperature. The unit of heat energy is the calorie.
Heat shock protein
A protein synthesized in response to an increase in temperature and which helps the cell to survive the stress. Examples of heat shock proteins are hsp60 and hsp70.
Heat soaked PCR
A strategy for increasing the specificity of PCR by incubating the template DNA at 94° for 30 minutes before adding Taq polymerase, dNTPs and primers.
Heat therapy
See thermotherapy
Heat-shock genes
A set of genes that are expressed when cells are subjected to a sudden rise in temperature. Many of these proteins encoded by the heat-shock genes function as chaperones that aid in the folding or unfolding of proteins.
Head-shock response element (HSE)
A specific nucleotides sequence in the promoter of the heat-shock genes (CNNGANNTCCNNG). Binding of a transcriptional enhancer protein to this sequence results in activation of the heat-shock genes.
Heavy chain (H chain)
The larger of the two polypeptides in an immunoglobulin molecule.
Heavy chain disease
Rare disorders that can be identified by the presence of α, γ or μ chains in plasma or urine. Certain monoclonal B-cell tumours produce only the heavy chains of immunoglobulins. The α-chain disease, which affects young adults of Mediterranean origin, is associated with gut lymphomas. The γ-chain disease affects the elderly and is characterised by lymphadenopathy and recurrent infections. The μ-chain disease is associated with chronic lymphatic leukaemia.
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