gene Related Biological Terms

An enzymic reaction that limits the rate of subsequent steps in its metabolic pathway. In a steady state the flux of metabolites, expressed as mmol/min, is the same for all steps. The step is usually characterized by thermodynamic irreversibility, and the enzyme has a Km that is low compared with levels of its substrate in vivo, thus insulating itself and the pathway from variations in substrate levels.

The synthesis of multiple copies of a specific gene, which remain as tandem repeats within the chromosome or are segregated as satellite DNA.

A method for the production of up to 1010 protein molecules per DNA by a continuous process in a homogeneous solution. Resto, E., Iida, A., Van Cleve, M.D. and Hecht, S.M. (1992) Nucleic Acids Res. 20, 5979-5983

The replacement of an allele during crossing- over owing to mismatch repair of the heteroduplex intermediate; rather than being equally represented in daughter DNA strands, one allele is over-represented and the other is under-represented. Partial repair can result in a hybrid or mosaic gene.

A method for quantification of the relative amount of a gene in a biological sample. One primer is constructed to hybridize with a gene known to be in the chromosome in question (e.g. chromosome 21 in the case of Down's syndrome) and another to hybridize to an unrelated gene in a different chromosome. Quantification of the amplified PCR products is sufficiently precise to distinguish a 50% increase in the chromosome 21 gene. Taylor, G.R. and Logan, W.P. (1995) Curr. Opin. Biotechnol. 6, 24-29

The inherited appearance of multiple copies of a gene. Duplication may result in identical or defective copies, either as tandem repeats at the original chromosomal locus, at a neighboring locus or at a completely different locus. Duplication may be benign or may be the basis of a pathology. If benign, one of the copies will be freed of any selective pressure and may evolve a new function.see gene amplification

(= hybridization probe)

The result of gene expression, i.e. an RNA or protein molecule.

The introduction of a homologous DNA sequence into a specific site in the genome of a cell, either by replacement of the former sequence, i.e. sequence replacement, or by insertion into the former sequence, i.e. sequence insertion. A vector that is homologous and co-linear with a partial sequence of the targeted gene is introduced into an appropriate cell, e.g. a stem cell of some sort; it is incorporated into the genome of some of the cell's progeny and replaces the former sequence. If, however, homologous regions of the vector hybridize to the gene, and it is then incorporated into the gene by homologous recombination, the result is a disruption of the gene by insertion of the vector sequence.

The in vivo introduction of a functional gene, and its expression, in the germ line cells (germ line therapy) or somatic cells (somatic gene therapy) of an individual who does not possess the normal gene. Mulligan, R.C. (1993) Science 260, 926-932