Teach yourself genetics / by R. J. Berry.

  • R. J. Berry
Date:
[1965], ©1965
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Teach yourself genetics / by R. J. Berry. Source: Wellcome Collection.

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    glossary 157 two corresponding loci of a pair of homologous chromo¬ somes (cf. heterozygous). Hybrid: The progeny of any pair of genetically different parents. Inversion: Reversal of a part of a chromosome resulting from two breaks in the same chromosome and rotation of the segment between them through 180° so that the genes within that part lie in inverse order. May be paracentric (where both breaks are on the same side of the centro¬ mere) or pericentric (where the two breaks are on opposite sides of the centromere). Linkage: The occurrence together of two or more genes on the same chromosome so that they are transmitted together from generation to generation, unless they are separated by crossing-over {q.v.). Locus: A particular position on a particular chromosome which always carries one of a particular series of allelo- morphic genes. Homologous chromosomes contain virtually identical sets of loci. Meiosis: Two successive cell divisions involving the re¬ duction of the number of chromosomes from the diploid (2и) to the haploid (и) number. Meiosis occurs at some time during the life cycle of all sexually reproducing organisms, usually during gamete formation. Mendel's Laws: First law of segregation, second law of independent assortment (see Chapter 2). Mitosis: The usual process by which cell nuclei divide into two with the formation of daughter nuclei having an identical chromosomal complement to that of the original nucleus. Mutagen: Any agent, chemical or physical, which may cause a mutation. Mutation: An inherited and relatively permanent change in a gene or chromosome set. Muton : The smallest element which can mutate. Probably is a single nucleotide pair. Non-Disjunction: The failure of the members of a