A cytogenetic analysis of meiotic drive in the mosquito, Aedes aegypti (L.)

Abstract

Meiotic drive in Aedes aegypti (L.) is shown by a Giemsa C-banding technique to be associated with. preferential isochromatid breakage of the X chromosome during male meiosis. These breaks remain open at least until anaphase-I and, since the range of cells affected is proportional to the sensitivity of the X chromosome to the Distorter gene, it is argued that they are directly related to the decreased number of spermatozoa found in distorting males. This reduction is considered to be attributable to the degeneration of more X-than Y-bearing spermatids but it is probable that some non-functional X-bearing spermatozoa are also produced. Chromosome breakage is almost completely confined to four sites, two adjacent to the centromere, one just proximal to the intercalary band and another about the centre of the unbanded arm. Although the first three of these lie within a region in which crossing-over does not take place, fragmentation occurs more frequently in a chiasmate arm than in one devoid of chromatid exchange.

Site-specific selfish genes as tools for the control and genetic engineering of natural populations

“…First, it has long been recognized that if a Y chromosome were to show TRD and spread to fixation in a population, then the sex ratio would become male biased, and if the TRD was extreme, then the population could be driven extinct for want of females (Hickey & Craig 1966;Hamilton 1967). In Aedes and Culex mosquitoes, there are Y chromosomes that somehow cause the X chromosome to break during the first meiotic division, and thus show TRD (Newton et al 1976;Sweeny & Barr 1978). Though the molecular mechanism is not yet known (the breaks may represent failed attempts at crossing-over), these observations suggest the following strategy.…”

More on recombination and selection in the modifier theory of sex-ratio distortion

“…Lessard (1987) generalized this model to include an arbitrary number of alleles at the sex-ratio modifying locus. Both treatments represent a simplification of the known biology of the situation in A. czgypti, and some of the genetically complicating phenomena have been described by Wood (1976) and Newton et al (1976Newton et al ( , 1978. In the studies by both Mafli and Jayakar, and Lessard, recursions were developed for the evolution of the chromosome frequencies in terms of the transmission probabilities of M-and m-bearing gametes from males, and the recombination fraction between the M/m and { Ai} loci.…”

Concerning RNA-Guided Gene Drives for the Alteration of Wild Populations

“…These "genetic load" drives would spread rapidly through minimally impaired heterozygotes when rare, and eventually cause the population to crash or even become extinct due to the accumulated load of recessive mutations. A second approach would mimic naturally occurring "meiotic" or "gametic" drives that bias the sex ratio 2,[48][49][50][51] . In this model, the Y chromosome (or its equivalent in other sex-determination systems) would encode an endonuclease that cuts and destroys the X chromosome during male meiosis, thereby ensuring that most viable sperm contain a Y chromosome 7,8,10,49,50 .…”

“…A second approach would mimic naturally occurring "meiotic" or "gametic" drives that bias the sex ratio 2,[48][49][50][51] . In this model, the Y chromosome (or its equivalent in other sex-determination systems) would encode an endonuclease that cuts and destroys the X chromosome during male meiosis, thereby ensuring that most viable sperm contain a Y chromosome 7,8,10,49,50 . The progressively dwindling number of females will culminate in a population crash or extinction 2,6,[52][53][54][55][56][57] .…”