However, this sex-determining gene is not present in all Oryzias species. The evolutionary events leading to this type of sex determination system are still unclear but, according to plant sex determination and sex chromosomes for females in Belleville data, it is possible to surmise that the mechanisms of sex-determining pathway evolution in fish are similar to the mechanisms taking place in insects.
Although the importance of certation has been controversial Carroll and Mulcahy ; Taylor et al. Qamar, H.
Smith BW Another theory has been presented by Saleh et al. Stehlik et al.
Isolation of male-specific cDNAs from developing flower buds or reproductive organs has not yet led to discovery of sex determining genes Matsunaga et al, ; Barbacar et al,probably because sex-determination happens very early in flower development Grant et al,so the genes identified are controlled in response to sex, rather than the controlling loci.
Charlesworth, D. Discussion With the availability of molecular techniques, we may now hope to understand more about how sex chromosomes evolve. Am Nat: — Lloyd, DG a. Once male sterility has reached a certain prevalence, then female sterility may have a chance to arise and spread.
The evolution of dioecy and plant sex chromosome systems.
Following the certation hypothesis Correns , discussed above, we predicted greater female bias in progeny sex ratios for females in which males were in closer proximity. Fertility and fitness of XO males in Drosophila I.
Volume 1: Lycopodiaceae to Platanaceae. The difference in seed sex ratios may reflect both life history and demographic differences between the species. Wrigley F