Mechanisms and genetic implications of 2n-gamete formation

Mechanisms and genetic implications of 2n-gamete formation

1984

REP.G1951

Gametes with the unreduced number (= 2n) of chromosomes may originate from different abnormal events during meiosis or arise in apomeiotic somatic cells of die ovule (apospory). Meiotic nuclear restitution leading to 2n-gametes may be associated with fused or parallel second metaphase spindles (First Division Restitution, FDR) or with incomplete second meiotic division (Second Division Restitution, SDR). Its association with failing or reduced homologous pairing leads to 2n-gametes which are genetically equivalent to FDR. The basic differences between FDR and SDR are described and explained. Several . mechanisms of 2n-gamete formation occurring in association with failing or reduced homol ogous pairing, as they occur in megaspore mother cells of apomictic species and in spore mother cells of synaptic mutants, interspecific hybrids, amphimonoploids, and anorthoploids, are described and discussed. Different mechanisms of 2n-gamete production are compared as to - their genetic implications. Data about genetic control of processes leading to 2n-gametes are presented along with a discussion on the effects of environmental factors on occurrence and frequency of 2n-gametes.

v.58(4):421-434, IOWA STATE JOURNAL OF RESEARCH

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