A Familial Centric Chromosome Fragment

199

104

In this paper a hypothesis is presented which relates chromosome pairing and sterility in males. This hypothesis has been formulated on the basis of data from numerous meiotic systems in the male of Drosophila melanogaster, where the sex chromosomes have heterochromatic pairing sites, sites which must interact in order for postmeiotic development to be normal. The predictions of this theory have been tested in three principal situations: (1) in various sex chromosome systems of man, the mouse, voles, and beetles; (2) in the B chromosome system of the grasshopper Myrmeleotettix maculatus; and (3) in univalent autosomal cases in man and in translocation heterozygotes of the mouse. In all three situations a striking correlation has been obtained between reduction or absence of pairing, on the one hand, and gametogenic breakdown, on the other. It is concluded that a saturation of pairing sites between homologous chromosomes, whether sex chromosomes or autosomes, is essential for regular meiotic or postmeiotic development.

Section: Discussionmentioning

confidence: 99%

Section: Autosomal Examplesmentioning

confidence: 99%

Sex-chromosome pairing and male fertility

Miklos¹

1974

199

104

“…Breakdown of spermatogenesis has been observed, for example, in individuals with an extra centric marker chromosome (Smith et al, 1965;H ulten et al, 1966;C handley, 1970), in individuals with an unbalanced form of a reciprocal autosome trans location (F redoa and R ayner, 1967), in a translocation mongol (H ulten and L indsten, 1970), and in an individual showing desynapsis of the bivalents at meiotic prophase (P earson et al, 1970).…”

Section: Discussionmentioning

confidence: 99%

Translocation heterozygosity and associated subfertility in man

Chandley¹,

Christie²,

Fletcher³

et al. 1972

Details of meiotic chromosome studies in four human male translocation heterozygotes are given. All are associated with subfertility. One Robertsonian translocation and one reciprocal autosome translocation appear to be associated with increased levels of abortion. Segregation of unbalanced gametic genomes is thought to be the underlying cause of fetal death. Two other reciprocal autosome translocations are associated with gametogenic failure, leading to azospermia in male heterozygotes.

“…1976: Searle ct al, 1978Chandlcy, 1981: Joseph andThomas. 1982;Johannisson et al in a person with a reciprocal 14:21 translocation, personal communication): ring chro mosomes (Mcllree ct al, 1966: Moreau andTeyssicr, 1982): bisatellited microchromosomes (Smith et al 1965: Hulten et al 1966: Kjessler. 1966Chandley, 1970: a reduction of fertility is indicated in the review by Steinbach ct al.…”

Section: Conditions Conducive To Chromosomally-derived Male Sterilitymentioning

confidence: 99%

Meiotic association between the XY chromosomes and unpaired autosomal elements as a cause of human male sterility

Rosenmann

Wahrman

Richler

et al. 1985

119

Intimate association between autosomal translocation trivalents and XY bivalents at pachytene was observed in a majority of cells of two men ascertained through primary sterility and found to be heterozygous for a 14;21 Robertsonian translocation. The association, studied by light and electron microscopy of spread first spermatocytes, was between the unpaired short arms of the normal chromosomes of the translocation trivalent and the differential axes of the XY chromosomes. In a minority of cells, this contact was not established, or not maintained, as alternative combinations between the elements available for non-homologous pairing were realized. Following a suggestion of Lifschytz and Lindsley (1972), sterility in these patients was attributed to spermatogenic arrest caused by physical contact of sex chromosomes with autosomal material and consequent interference with the normal metabolism of the sex chromosomes. Autosomal aberrations and polymorphisms, which lead to the presence of unpaired segments at meiosis, may thus play a critical role in a general mechanism of chromosomally-derived male sterility. It is proposed that such a mechanism may also be instrumental in the initiation of reproductive barriers in nature.