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Chromosomes Crossing over

Early in the first meiotic division the extended chromosomes double (replication of DNA) and homologous chromosomes pair each chromatid pairs with a chromatid in the other homologous chromosome crossing-over takes place... [Pg.592]

Figure 36-9. The process of crossing-over between homologous metaphase chromosomes to generate recombinant chromosomes. See also Figure 36-12. Figure 36-9. The process of crossing-over between homologous metaphase chromosomes to generate recombinant chromosomes. See also Figure 36-12.
Crossing over The breaking of one maternal and one paternal chromosome during meiosis with exchange of corresponding sections of DNA, and rejoining of the chromosomes. The process leads to an exchange of alleles between chromosomes and is the fundamental principle of human evolution (see also recombination). [Pg.532]

Recombination The process by which progeny derive a combination of genes different from that of either parent In higher organisms, this is achieved by crossing over of chromosomes. [Pg.537]

Crebelli R, Bellincampi D, Conti G, et al. 1986. A comparative study on selected chemical carcinogens for chromosome malsegregation, mitotic crossing-over and forward mutation induction in Aspergillus nidulans. Mutat Res 172 139-149. [Pg.132]

Meiosis is cell division that produces two daughter cells with only half the number of chromosomes of the parent cell these are haploid cells. It occurs during the formation of spermatozoa and ova. The normal number of chromosomes is then achieved at fertilisation of an ovum by a spermatozoon. Meiosis also results in crossing over , which is the physical reciprocal exchange of parts... [Pg.451]

As previously summarized, diethyl sulfate induced mutation and DNA damage in bacteria and induced reverse mutation and mitotic recombination in yeast. In plant cells, diethyl sulfate induced chromosomal aberrations. In a single study, diethyl sulfate did not induce heritable translocation in Drosophila melanogaster but did induce autosomal recessive lethal mutations, sex-linked recessive lethal mutations and genetic crossing-over. In cultured mammalian cells, diethyl sulfate induced chromosomal aberrations, mieronueleus formation, sister chromatid exchanges, forward mutation and DNA singlestrand breaks it also induced unscheduled DNA synthesis in primary cultures of rat... [Pg.1407]

During the prophase of the first meiotic division (meiosis I) two homologous pairs of partially "condensed" chromosomes must find each other and pair with appropriate orientation. A protein in the telomeres of the chromosomes seems to be involved.269 277 The key structure in meiotic crossing-over is the ribbonlike synaptonemal complex formed by the pairs of homologous chroma fids.271/278 2791 This complex, in which a proteinaceous core or axial element separates the greatly extended chromatid pairs (Fig. 26-13), is fully formed in the pachytene stage of meiosis. Formation of the synaptonemal complex is preceded by development of a few double-stranded breaks in... [Pg.1505]


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See also in sourсe #XX -- [ Pg.86 ]




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Cross over

Crossing-over

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