| genes, immunoglobulin | Genes encoding the light and heavy chain segments of immunoglobulins. Light chain gene segments are symbolised l-v (variable), j (joining) and c (constant); ig heavy chain segments have, in addition, a diversity (d) gene. Each segment codes for certain amino acids, and each has a different nucleotide sequence; the genes are assembled by a remarkable shuffling of the segments during b lymphocyte maturation. (12 Dec 1998) |
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| genes, insect | The hereditary material of insects. (12 Dec 1998) |
| genes, intracisternal a-particle | A family of retrovirus-like genetic elements coding for virus-like particles found regularly in early rodent embryos (2-cell to blastocyst stage), but which, under certain circumstances such as DNA hypomethylation, are transcribed in a wide variety of neoplasms, including plasmacytomas, neuroblastomas, rhabdomyosarcomas, teratocarcinomas, and colon carcinomas. (12 Dec 1998) |
| genes, jun | Retrovirus-associated DNA sequences (jun) originally isolated from the avian sarcoma virus 17 (asv 17). The proto-oncogene jun (c-jun) codes for a nuclear protein which is involved in growth-related transcriptional control. Insertion of c-jun into asv-17 or the constitutive expression of the c-jun protein produces tumourgenicity. The human c-jun gene is located at 1p31-32 on the short arm of chromosome 1. (12 Dec 1998) |
| genes, lethal | Genes which result in the premature death of the organism; dominant lethal genes kill heterozygotes, whereas recessive lethal genes kill only homozygotes. (12 Dec 1998) |
| genes, mcc | Tumour suppressor genes located in the 5q21 region on the long arm of human chromosome 5. The mutation of these genes is associated with the formation of colourectal cancer (mcc stands for mutated in colourectal cancer). (12 Dec 1998) |
| genes, mdr | Genes responsible for multidrug resistance resulting from their overexpression in mammalian cells. Mammalian p-glycoproteins are encoded by small mdr gene familes. The human multidrug resistance 1 (mdr1) gene responds to environmental stress including various anticancer agents. It is a major determinant in the development of resistance to a large number of cancer chemotherapeutic agents. (biochem biophys res commun 1994;199(3):1428-35; cancer res 1994:54(6):1536-41) (12 Dec 1998) |
| genes, MHC class I | Genetic loci in the vertebrate major histocompatibility complex which encode polymorphic characteristics not related to immune responsiveness or complement activity, e.g., b loci (chicken), dla (dog), gpla (guinea pig), h-2 (mouse), rt-1 (rat), HLA-a, -b, and -c class I genes of man. (12 Dec 1998) |
| genes, MHC class II | Genetic loci in the vertebrate major histocompatibility complex that encode polymorphic products which control the immune response to specific antigens. The genes are found in the HLA-d region in humans and in the I region in mice. (12 Dec 1998) |
| genes, mos | Retrovirus-associated DNA sequences (mos) originally isolated from the moloney murine sarcoma virus (mo-msv). The proto-oncogene mos (c-mos) codes for a protein which is a member of the serine kinase family. There is no evidence as yet that human c-mos can become transformed or has a role in human cancer. However, in mice, activation can occur when the retrovirus-like intracisternal a-particle inserts itself near the c-mos sequence. The human c-mos gene is located at 8q22 on the long arm of chromosome 8. (12 Dec 1998) |
| genes, myc | Family of retrovirus-associated DNA sequences (myc) originally isolated from an avian myelocytomatosis virus. The proto-oncogene myc (c-myc) codes for a nuclear protein which is involved in nucleic acid metabolism and in mediating the cellular response to growth factors. Truncation of the first exon, which appears to regulate c-myc expression, is crucial for tumourigenicity. The human c-myc gene is located at 8q24 on the long arm of chromosome 8. (12 Dec 1998) |
| genes, nef | DNA sequences that form the coding region for a protein that down-regulates the expression of human immunodeficiency virus (HIV). Nef is short for negative factor. (12 Dec 1998) |
| genes, neurofibromatosis 1 | Tumour suppressor genes located on the long arm of human chromosome 17 in the region 17q11.2. Mutation of these genes is thought to cause neurofibromatosis 1. (12 Dec 1998) |
| genes, neurofibromatosis 2 | Tumour suppressor genes located on the long arm of human chromosome 22. Mutation or loss of these genes causes neurofibromatosis 2. (12 Dec 1998) |
| genes, nitrogen fixation | Regulatory and structural genes present in certain bacteria, algae and fungi that control the conversion of atmospheric nitrogen into biologically usable compounds; include nif structural genes (e.g., nifd, nifh) for nitrogenase and nitrate reductase as well as regulator genes nifa, nifb, ntra, ntrb, ntrc. Some are responsible for regulating transcription of genes involved in the assimilation of poor nitrogen sources in enteric bacteria. (12 Dec 1998) |