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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Homology Modelling - Artificial Chromosome

Homology modeling
The use of 3 dimensional geometry and sequence information from proteins with known structure to predict the structure of a protein whose 3 D structure is unknown. This involves search and alignment algorithms to find the best sequence overlap followed by use of the 3D structure model of the conserved regions of the unknown protein. The variable regions of the unknown protein are then modeled using a variety of computational techniques.

Homomultimeric protein 
A protein containing identical subunits.

Hoogsteen  pairing
Non Watson Crick base pairing that allows the formation of triple helical DNA. Hoogsteen pairs have also been identified in tRNA. The Hoogsteen pairs are not isomorphous with the W C pairs and have an 800 angle between the glycosidic bonds and an 8.6 A0 separation of the anomeric carbons.

Hoogteen positions
 The atom N7,O6 and N6 of purines that participate in H bonding in triplex DNA.

Horizontal transfer
The transfer of genetic material between two distinct species that do not normally exchange genetic material. The transferred DNA is incorporated into the recipient genome and can be detected by a noval phylogenetics history and codon content compared to the rest of the genome.

Hormone
A substance secreted by an endocrine gland that is transported by circulation to another tissue or gland whose function it regulates. Hormones mediate their biological effects by binding to specific receptors present on the target cells. Binding of the hormone to the receptors is highly specific, saturable and readily reversible. The receptor has high affinity for the hormone. The receptors which are proteins, contain two functional domains a recognition domain binds the hormone, and a coupling domain couples bound hormone to some intracellular function (signal transduction).

Hox complex
Two tightly linked clusters of genes found in Drosophila (bithorax and Antennapedia complexes) that regulate the differences between the different body segments. Homologous Hox complexes are also found in other animals.

Hox genes
Clusters of mammalian genes containing homeboxes. The individual members are related to the genes ANT C and BX C in Drosophila melanogaster.

Horizontal genetic transmission
 Introduction of genetic information into a cell from an exogenous source.

HPLC
See high performance liquid chromatography.

HTGS (HTG) High throughput genome sequences
A division of databases that contains the unfinished sequences that are the result of sequencing efforts inhuman and other higher organism. These sequence contains gaps. HTG sequence entries undergo a maturation process. In phase 1, the entry contains unfinished sequences that are the result of  sequencing efforts in human and other higher organism. These sequences contain gaps. HTG sequence entries undergo a maturation process. In phase 0, the entry contains from single to a few pass read of a single clone. In Phase 1, the entry contains unfinished sequence that may be unordered, contain unoriented contigs, or a large number of gaps. In Phase 2, the entry still contains unfinished sequence but is ordered, with oriented contigs, with no gaps. At this point, the entry is move into the appropriate primary GenBank division.

Homoplasy
Similarity that has evolved independently and not indicative of a common phylogenetics origin.

Homoploid
possessing a chromosome number that is typical of the species

Homopolymer
A polymer composed of a single type of monomer. For example, polyuridylate, polyphenylalanine.

Homopolymeric tailing
See tailing

Homopolysaccharides
A polysaccharide containing only one type of monosaccharides unit.

Homothallic plants
 Plants in which both male and female sex cells are produced enabling self fertilisation.

Homotropic
 Refers to an allosteric modulator that is identical to the normal ligand.

Homotropic enzyme
An allosteric enzyme that uses its substrate as a modulator.

Homozygote
An individual who has two copies of the same allele at a particular locus on  homologous chromosome.

Hormone receptor
 A protein which binds a specific hormone initiating a cellular response.

Hormone response element
(HRE) A short sequence of DNA to which receptors for steroid, thyroid, retinoid and vitamin hormones bind and alter the expression of contiguous genes. Each hormone has a consensus sequence that is preferred by the cognate receptor.

Host
1. An organism used for multiplication of rDNA molecules. 2. Computers on the internet that can be addressed directly the unique IP address.

Host specific toxin
A metabolite produced by a pathogen that has a host specificity equivalent to that of the pathogen. Such toxins are used for in vitro selection experiments to screen for tolerance or resistance to the pathogen.

Hotspot A site at which the frequency of recombination or mutation is very high.

Hostart PCR
A strategy for increasing the specificity of PCB by heating the template, dNTPs and primer mix to 80-850 C before adding Taq polymerase.

House keeping gene
A gene that serves a function in all the cell types of an organism, irrespective of their function. See constitutive genes.

Homoplasmic
From Homozygous cytoplasm. An individual with organelles of uniform genotype.

Homoplasmy
A condition in which all copies of an organelle are genetically identical.

HTLV
An acronym for Human T cell Leukaemia Virus. A group of human retroviruses that cause human T cell leukaemia.

HTML
 Hypertext markup language. The markup language that controls how text and multimedia objects are displayed on web pages.

HTTP
 Hypertext transfer protocol. The method used to exchange information over the World Wide Web.

HUGO
 The Human Genome Organisation

Human Anti Murine Antibody Response (HAMA)
 An immune response generated in humans to antibodies raised in mouse or rat (murine) cells

Human Artificial Chromosome (HAC)
 A high capacity cloning vector constructed like human chromosome. HACs are used to transfer or express large fragments of human DNA.

Human Chorionic Gonadotrophin (hCG)
The gonadotrophic hormone produced by the human placenta. It is a glycoprotein with structural homology to LH. hCG is involved in the maintenance of corpus luteum during the first four to six weeks of pregnancy. The determination of serum or urine hCG is useful as a pregnancy test. Increased level of hCG are seen in malignancies such as chorionepithelioma an testicular tumours. Ectopic production of hCG by non trophoblastic tumours occurs in hecatombs and lung carcinomas.
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