Although nullisomy is a lethal condition in diploids, an organism such as bread wheat, which behaves meiotically like a diploid although it is a hexaploidcan tolerate nullisomy. The four homoeologous chromosomes apparently compensate for a missing pair of homologs.
Dosage compensation and MSCI are fields of intense current study, currently in a state of flux. Tesarik, J.
XY and ZW: is meiotic sex chromosome evolution inactivation the rule in evolution. Despite this uncertainty, we can have confidence that these processes have major effects on the evolution of sex chromosomes, more than what had been previously recognized.
In many organisms, one sex chromosome usually the Y or the W is missing a large proportion of the genes of the other.
Motulsky, Human Genetics. NCBI Bookshelf. We then review recent studies that find genes that are more strongly expressed in one sex than the other tend to be found on sex chromosomes much more or much less often than expected. Molecular studies on the origin of trisomy for chromosomes 2—12, 13—15, 16, 18, 21, 22, XXY and XXX in informative concepti showed Gene action in the X chromosome of the mouse Mus musculus L.
Citing articles via Web of Science Even at putatively neutral sites, loci on different sex chromosomes evolve at different rates. In these large flightless birds, the Z and W are nearly identical. Several genes that are known to contribute to hybrid incompatibility are heterochromatic or interact with heterochromatin.