at Related Biological Terms

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

Gene duplication leads to the generation of a new copy of a gene or chromosome region. Gene duplication is a widespread mutation mechanism occurring in all multicellular organisms (e.g., metazoa and plants) and microorganisms that have been critical for evolution. For example, a whole-genome duplication event occurred in the common ancestor of all teleost fishes contributing to the rich diversity of this vertebrate group. Gene duplication may occur through different mechanisms. For example, during recombination events in meiosis, unequal crossing-over between misaligned homologous chromosomes leads to tandem duplication. In replication slippage, a mistake in DNA replication by the polymerase, often over repetitive sequences, leads to the duplication of short sequences and their misalignment. In aneuploidy, a nondisjunction at a chromosome leads to the wrong number of chromosomes (e.g., trisomy 21) Learn more about restriction enzymes.

Recombination between homologous chromosomes that may occur during meiosis anywhere along their lengths. (see also Holliday model; Meselson-Radding model)

A DNA sequencing method that involves PCR amplification of the target and uses a primer with an attached phage promoter sequence, transcription to produce a single-stranded RNA and reverse transcription with dideoxy terminator nucleotides that upon electrophoresis will generate a sequencing ladder. Buerstedde, J.-M. and Sommer, S.S. (1991) in PCR Topics: Usage of Polymerase Chain Reaction in Genetic and Infectious Diseases (Rolfs, A., Schumacher, H.C. and Marx, P., eds.), pp. 9-14, Springer-Verlag, Berlin Recommended reading: next generation sequencing

A method to detect and isolate DNA sequences that are candidate genes for inherited disorders for which the gene product is unknown, based on the absence of mismatches in DNA sequences between an affected individual and a heterozygous or carrier progenitor. Large DNA segments are prepared from the genomic DNA of the two related individuals in such a way (e.g. by leaving 3'-overhangs) that they will not be degraded by subsequent exonuclease digestion, e.g. by ExoIII. The DNA from one individual is enzymically methylated and annealed with the DNA of the second, heterohybrids (two methylated or two unmethylated strands) are cleaved by appropriate endonucleases, e.g. DpnI and MboI, and the uncleaved duplexes are scanned for single-base mismatches by methyl-directed mismatch repair enzymes that leave single-strand nicks that are attacked by ExoIII. The duplexes that survive all these tests are those that are shared by the two related individuals and are therefore candidates for the affected gene. Nelson, S.F., McCusker, J.H., Sander, M.A., et al. (1993) Nature genet. 4, 11-17; Kolodner, R.D. (1995) Trends Biochem. Sci. 20, 387-401 Recommended reading: next generation sequencing

A metabolite that regulates many operons, e.g. glucose, as it regulates several anabolic reactions in a bacterium.

A series of operons that are induced together, e.g. the genes for the heat-shock proteins or those for the SOS repair proteins.

The reversible condensation of the carbonyl group of a sugar with an amino group of a protein to form a Schiff base that often triggers subsequent irreversible rearrangements, e.g. the condensation of glucose with haemoglobin A to form haemoglobin A1c.

A compound composed of an oligosaccharide linked to a protein or lipid, e.g. mucins (which are glycoproteins), globosides (which are N-acetylsphingosine conjugates of oligosaccharides), and the endotoxin of Gram-negative bacteria. (see also lipopolysaccharide (LPS))