[A model of regulation of crossing over].
Very high variability is characteristic of crossing over. A mechanism of crossing-over variation is proposed on the basis of new data obtained by Chadov et al. Variations are believed to be determined by the character of pairing preceding crossing over and the mechanism of transforming contacts into exchanges. Pairing of homologues is assumed to involve consecutive formation of local contacts between them. The onset of this process depends of the chromosome structure. Exchanges appear in contact sites. Determination of crossing-over sites occurs when the contact number in a meiocyte reaches a certain threshold. The number of contacts formed in each chromosome pair by this time can vary. This results in variations of all parameters of crossing over: recombinational length (RL), exchange number per chromosome arm, and interference. The effect of a chromosome aberration on crossing over in aberrant and heterologous chromosome pairs, i.e., the interchromosomal effect on crossing over (IEC) and the mechanisms determining exchange number and interference, are explained on the basis of the proposed model.
Chadov
B F
BF
D000818:Animals; D003434:Crossing Over, Genetic; D005260:Female; D008957:Models, Genetic