Cytological mapping of the M and D loci in the mosquito, Aedes aegypti (L.)

Abstract

The separate identities of the male-determining factor, M, and the sex-linked Distorter gene, D, are established in an Accra strain ofAedes aegypti. Their positions in the Y chromosome are defined in relation to each other and to Giemsa C-bands. Thus, M is invariably inherited with the centromere, whereas D lies towards the intercalary band. Approximately 1.2% recombination occurs between M and D but, in a chromosome known for its distal localization of chiasmata, it is argued that the two are not necessarily as closely linked cytologically as this might imply. Evidence on the genetic effects of recombina. tion in the region of M and D is also considered.

Calcium release from calmodulin and its C‐terminal or N‐terminal halves in the presence of the calmodulin antagonists phenoxybenzamine and melittin measured by stopped‐flow fluorescence with Quin 2 and intrinsic tyrosine

“…Calmodulin fragments 1 -77 and 78 -148 were prepared by limited trypsin digestion according to Drabikowski et al [38] and Newton et al [39] in the presence of calcium as described previously [29]. Digestion was carried out at 30 "C, pH 8.0 for 45-50 min in a medium containing 5 mM NH4HC03, 50 mM NaCI, 2 mM CaCl,, 2.5 mg calmodulin/ ml, 38 pg trypsin/ml (calmodulin/trypsin ratio 65).…”

“…With this procedure undigested calmodulin is eluted approximately 14 rnin after fragment 1 -77 [29]. The calmodulin fragments 1 -77 and 78 -148 separated by the above precedure are probably not homogeneous; fragment 1 -77 may contain fragments 1 -74 and 1-75 [39] and fragment 78-148 is probably contaminated by fragments 75-148 and 76-148 [39,401. It is thought, however, that this slight heterogeneity has no influence on the present results and for simplicity of presentation only the terms fragment 1 -77 and fragment 78 -148 are used.…”

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.…”

Selected lines of Aedes aegypti with persistently distorted sex ratios

“…Recent studies have been carried out to investigate the abnormalities by electron microscopy (Owusu-Daaku, 1994). The present study was in support of that work, aimed at recreating the crosses of Newton et al (1976Newton et al ( , 1978. The Chipei strain was no longer under culture and fresh supplies could not be obtained, so it was necessary to produce a highly sensitive strain by selection.…”