Many Silene species are gynodioecious and others are hermaphroditic. The process may sometimes have been more gradual, with partial sterility mutations Lloyd, a ; Charlesworth and Charlesworth, b. The effect of hitchhiking on genes linked to a balanced polymorphism in a subdivided population.
Figure 1. Consistent with theoretical models for the evolutionary transition from hermaphroditism to monoecy, multiple sex determining genes are involved, including male-sterility and female-sterility factors. Our understanding of the evolution of plant sex chromosomes and sex determination should be advanced by the use of molecular markers, so several groups are searching for these.
Sinauer: Sunderland, Mass, pp — The availability of closely related species, probably with chromosomes having gene content similar to that of the ancestral sex chromosomes, should show how genes have evolved since becoming sex-linked, offering a system to test between the different hypotheses.
Both X- and Y-linked expressed loci have now been identified in S. Evolution of reproductive systems in the genus Silene.
The human Y chromosome derives largely from a single autosomal region added to the sex chromosomes 80— million years ago. Larger samples from within single populations are therefore needed. The chloroplasts contain chlorophylla pigment that allows plants to make their own food in the form of glucose since plants cannot eat.
This means that every bacterium, in the absence of chance DNA mutations, is genetically identical to its "parent" and any "children" it may have.
Am J Bot , 80 : — Continuous variation in Y-chromosome structure of Rumex acetosa. Figure 1.