General cytogenetics / J. Sybenga.

  • Sybenga, J. (Jacob), 1926-
Date:
1972
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: General cytogenetics / J. Sybenga. Source: Wellcome Collection.

    143/384 page 125
    §2.9 Recombination 125 О А А и Fig.2.17. Genetically determined chiasma localization in rye. (A,В) The usual terminal localization of chiasmata at metaphase I in normal rye (Secale cereale), where only occasionally figures like С and D are seen, while the other types are quite infrequent. C, D, E, F are Ml bivalents with terminal and proximal chiasmata as occur quite frequently in abnormal genotypes derived from intercrossing different species related to S.cereale (Jones, 1967). lated along with lines that had lost this property and that had a random distribution (fig.2.17). Apparently genes regulating locali¬ zation had segregated. To what extent this regulation acts through chromosome pairing is not known, but many instances have been found of an effect of pairing on chiasma formation (section 2.9.1). 2.9. Factors affecting chiasma formation and crossing-over 2.9.1. Interference and chromosome pairing Interference (section 2.8.1). including interchromosome effects (section 2.8.4) are factors that affect genetic exchange. It is quite probable that several of the factors mentioned below affect chias¬ ma formation and crossing-over by way of their effect on interfer¬ ence. The same is true for chromosome pairing: variations in the extent of pairing are common and are closely correlated with vari- Ь ^ üic ВС DE
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