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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Hepatitis D (HDV, Delta Agent) - Heterohypekomers
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Hepatitis B (HBV)
Also called serum hepatitis. It occurs due to percutaneous (needle stick), sexual or perinatal transmission. It can be diagnosed by the presence of viral surface antigen (HBsAg) and an internal component of the virus (HBcAg) in the serum soon after infection, followed by appearance of serum antibodies anti-HBs and anti-HBc after a few weeks. Detection of HBV DNA in serum is the most sensitive test.
Hepatitis C (HCV)
Also called non-A, non-B hepatitis. It is transmitted by percutaneous transmission and intravenous drug use. It is detected by the presence of anti-HCV in serum.
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Hepatitis D (HDV, Delta Agent)
Hepatitis that is endemic among HBV carriers in the Mediterranean basin and areas of South America. It is also transmitted percutaneously in HBsAg-positive intravenous drug users or by transfusion in haemophiliacs. Patients are detected by anti-HDV in serum.
Hepatitis E (HEV)
Hepatitis that is responsible for water-borne epidemics of hepatitis in India, Mexico and parts of Asia and Africa. It is detected by the presence of anti-HDV in serum.
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Hepatocyte
The major cell type found in the liver.
Hepatoma
Liver tumour.
Hepatomegaly
Enlargement of the liver.
Heptad repeat
A trandemly repeated sequences of seven amino acids found in intermediate filament proteins.
Heredity
Transmission of traits from parents to offspring.
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Herbicide
A substance that is toxic to plants. The term is used for agrochemicals that are used to kill specific unwanted plants, such as weeds.
Herbicide resistance
The ability of a plant to tolerate herbicides. When a herbicide is sprayed onto a field planted with such resistant crops, all the plants except the crop would be killed. This is an effective method of weed control that obviates the need to develop herbicides specific to each weed type. There are several concerns about the widespread use of this technology: chiefly the increased use of herbicides, and the possibility that resistant crop plants will escape to become weeds, or that their resistant genes could be transferred to other species, including weeds.
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Hereditary cancer
Cancer that occurs as a result of inheritance of a mutated gene within a family.
Hereditary coproporphyria
An autosomal dominant disorder characterised by a partial deficiency of coproporphyrinogen Oxidase, which converts coproporphyrinogen III to protoporphyrinogen IX.
Hereditary disease
See genetic disease.
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Hereditary fructose intolerance
An autosomal recessive disorder due to deficiency of fructose 1-phosphate aldolase (aldolase B). Due to the enzyme block, there is accumulation of fructose-1-phosphate in tissues. The clinical manifestations include liver disease, renal tubular damage and hypoglycaemia. Hypoglycamia may be due to inhibition of glycogenolysis. Deposition of fructose 1-phosphate in liver causes hepatomegaly with jaundice. Progressive liver damage can lead to cirrhosis and ascites. Treatment involves intake of low fructose diet.
Hereditary nonpolyposis colon cancer (HNPCC)
A condition that predisposes to the development of colorectal cancer. HNPCC is associated with microsatellite instability due to defects in the mismatch repair (MMR) genes hMSH2, hMLHI and hPMS2.
Hereditary spherocytosis
A hereditary form of anaemia characterised by abnormally shaped red blood cells that are spherical and abnormally fragile landing to haemolytic anaemia.
Herpes
A family of large DNA viruses that infect humans and cause infections diseases such as chicken pox and shingles. Members of the family include Herpes simplex, Varicella zoster, cytomegalovirus and Epstein-Barr virus.
Herpes simplex virus (HSV)
A member of the herpes family of viruses that has been implicated in the pathogenesis of cervical and oral cancers.
Hers' disease (glycogen storage disease type VI)
A rare, glycogen storage disease due to liver phosphorylase deficiency. The disease is characterized by hepatomegaly and hypoglycaemia with high glycogen content in the liver.
Hershey-Chase experiment
A classic experiment conducted by Martha Hershey and Alfred Chase in 1952 to demonstrate that DNA is the genetic material. In this experiment, bacteriophages containing 32P-labelled DNA and 35S-labelled protein were allowed to infect bacterial cells. After several minutes, the bacteriophages attached to the bacteria were separated by strong mechanical agitation. It was found that 32P label and not the 35S label had entered the host bacteria indicating that only the viral DNA enters the host cell.
Heteroalleles
Mutations which are functionally allelic but structurally non-allelic; mutations at different sites in a gene.
Heterocaryon
See heterokaryon
Heterochromatin
Transcriptionally inactive chromatin. These regions stain darkly.
Heterodimer
A protein composed of two different polypeptide chains.
Heteroduplex
A double-stranded nucleic acid molecule formed as a result of base pairing between two similar but not identical strands. The two DNA strands may not have perfect complementarity. Some regions of the heteroduplex will remain single stranded. Such structures can result due to mutation, recombination or annealing of complementary single-stranded DNAs.
Heteroduplex analysis
A method for the detection of gene mutations by mixing PCR-amplified mutant and wild-type DNA followed by denaturation and reannealing. The resultant products are resolved by gel electrophoresis, and single base substitutions detected under optimal electrophoretic conditions and gel formulations. Large base pair mismatches may also be analysed by using electron microscopy to visualise heteroduplex regions.
Heteroduplex mapping
A technique used to determine the location of a particular nucleotide sequence in a nucleic acid molecule by generating a heteroduplex between the nucleic acid to be mapped and a reference nucleic acid strand.
Heterofermentation (heterolactic fermentation)
Fermentation characteristic of enteric bacteria in which only part of the fermentation product is lactic acid which the other part is formate and acetyl CoA.
Heterogametic sex
Having the diploid chromosome constitution 2A + XY.
Heterogeneity
See genetic heterogeneity.
Heterogenous nuclear RNA (hnRNA)
The initial transcript present in the eukaryotic nucleus. It contains introns and is further processed to form mature RNA.
Heterogenous system
A system in which two or more different phases are separated from one another by defined boundaries. For example, ice in contact with water.
Heterohypekomers
Isoschizomers that differ in methylation sensitivity used for mapping methylated DNA. For example, although both Hpall and Mspl recognise the sequence CCGG, only Hpall is sensitive to methylated CpG motifs in higher eukaryotes.
Heterokaryon
A cell containing two or more nuclei in a common cytoplasm. This is produced by fusing somatic cells.
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