In a diploid chromosome complement the homologous members are structurally equivalent throughout their entire length and since pairing at meiosis is both qualitatively and quantitatively limited to structurally homologous pairs only bivalents are formed. Thus in the basic meiotic system structural homology is one of the conditions for regular pairing and hence regular segregation. Such structural homology of course is not a requirement for regular mitotic separation since here each chromosome behaves quite independently of all others whether these are homologous with it or no. But at meiosis the situation is quite different for with a change in structural homology there are likely to be problems in pairing and, following any modification in the pattern of pairing, further complications are introduced by chiasma formation.
KeywordsAlternate Orientation Chiasma Frequency Chiasma Formation Inverted Duplication Ovule Abortion
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