Dictionary,Defintion,Meaning,What is Coisogenic or Congenic, Complementation Genetics, Colchicine, Common Ancestor, Comparative Biology

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Home >> Genetics Dictionary >> Coisogenic or congenic - Complementation

Your Ad Here	Coisogenic or congenic Nearly identical strains of an organism; they vary at on single locus. Colchicine An alkaloid that inhibits the formation of the spindle delays the division of centromeres; used to produce polyp varieties of horticulturally important species; also used to stop mitosis at metaphase for preparation of karyotypes. Common ancestor The most recent ancestral form or species from which two different species evolved.
Comparative biology The study of patterns among more than one species. Comparative genomics. The study of human genetics by comparisons with model organisms such as mice, the fruit fly, and the bacterium E. Comparative method The study of adaptation by comparing many species Complementary DNA (cDNA) DNA that is synthesized in the laboratory from a messenger RNA template.
Complementary sequence Nucleic acid base sequence that can form a double-stranded structure with another DNA fragment by following h pairing rules (A pairs with T and C with G). complementary sequence to GTAC for example, is CATG. Complementarity Chemical affinity between nitrogenous bases as a result of hydrogen bonding. Adenine is complementary to thymine, and cytosine is complementary to guanine. Complementarity is necessary for base pairing in double-stranded DNA. Complementation (genetics) The complementary action of different genetic factors. The term usually implies two homologous chromosomes or chromosome sets, each defective because of mutation and unable by itself to promote the normal development or metabolism of the organism, but able to do so jointly when brought together in the same cell.	Your Ad Here
Methods for testing In a diploid organism, such as a flowering plant or an animal, in which there are two sets of chromosomes in each cell nucleus, one can test for complementation by crossing mutant strains and observing whether or not the hybrid progeny are mutant in character. In fungi, which are usually haploid (one set of chromosomes in each nucleus), complementation tests can often be made by forming heterokaryons, in which two different kinds of nuclei are present together in the same cell. In bacteria, which are haploid with only one chromosome, there are techniques for introducing an additional chromosome fragment into a cell in order to test the fragment's ability to complement the chromosome already present. Test analysis
Your Ad Here	Complementation tests are used to investigate the relationships between different genetic mutations which individually cause various functional defects in the organism such as failures of growth or development. If mutations a and b are at different sites in the same chromosome, a+ and b+ being the, corresponding nonmutant sites, a complementation test involves making the chromosome combination ab+ / a+b. This is called the trans configuration. In principle it can be compared to the situation in which both mutations are present in one chromosome and both normal sites in the other (the cis configuration) ab/a+b+. If a+ and b+ act independently, the is and trans arrangements should both give a nondefective organism, since both contain both a+ and b+. If, on the contrary, a and b are within a functionally indivisible unit, cis will be normal but trans mutant (no complementation).

Noncomplementary units S. Benzer proposed the term cistron for the unit within which mutants do not complement each other. The word gen often used in the same sense. The usual biochemical function of a cistron, or gene, is to determine the structure of a specific polypeptide component of a protein. Full complementation between different genes is the rule except when, as sometimes in bacteria, the genes form part of a functionally coordinated complex (operon). Allelic mutants (mutants within one gene) show limited complementation in some cases, for example when certain pairs of mutant polypeptides correct each other's defects through coaggregation in a complex protein

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