Model of sex chromosome evolution theory in Thornton

The gene content of the X chromosome and the Z chromosome is unusual, with a non-random representation of genes with sex-biased gene expression. Investigations of organisms with sex chromosomes being in the early stages of degeneration can help to solve the discussed problems.

Random deaths in a computational model for age-structured populations. Paucity of genes on the Drosophila X chromosome showing male-biased expression.

model of sex chromosome evolution theory in Thornton

Granulosa cells Somatic cells in the ovary that surround the oocyte. Can intra-Y gene conversion oppose the degeneration of the human Y chromosome? SJ was truncated and appeared to be non-functional and was therefore classified as a pseudo-retrogene.

Model of sex chromosome evolution theory in Thornton

Note that we excluded pseudogenes from the analysis in most cases, the only exceptions being two female pseudogenes that belong to gametologue pairs, which were included to provide complete information about the model of sex chromosome evolution theory in Thornton of these gametologue pairs across species Additional file 1 : Table S1.

If the ancestral system was indeed X0, this would support the idea that the Drosophila Y was acquired only secondarily and is not a degenerate X. Thus, this model simulates the case in which many mutations being neutral for young individuals can be passively accumulating over generations leading to senescence and death because of deleterious effects Sign up.

Sex-biased transmission of X and Y chromosomes implies opportunity for sexually antagonistic selection to redistribute male- and female-beneficial mutations, and for genetic conflicts over sex ratios to arise Insects with this type of sex determination include Drosophila and Anopheles.

Empirical data to test models of Y degeneration are scarce. The most parsimonious scenario would thus be that the Ectocarpus species lost the female gametologue whereas the kelp species lost the male. To our knowledge, it is currently unknown whether a fast Z effect exists in insects with female heterogameity.

Model of sex chromosome evolution theory in Thornton

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  • Apr 21,  · The classic model for sex chromosome evolution in plants is slightly different from that outlined above. Instead of a single locus initiating the development of one sex, the plant model requires two linked loci, one each for female and male sterility (Westergaard ; Charlesworth and Charlesworth ). This difference results from the fact that most sex chromosomes in plants originate in monoecious or hermaphroditic lineages where both sexes Cited by: 5. Sex chromosomes have evolved independently many times in different groups of organisms, including plants, nematodes, Drosophila, butterflies, birds, and mammals (Ohno ; Bull ).The best-studied Y-chromosomes to date are those of humans and Drosophila melanogaster (Lahn et al. ; Carvalho ).These highly derived Y-chromosomes retain few functional genes, and consist of a large Cited by:
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  • Feb 08,  · Sex-chromosome evolution. A consensus model for sex-chromosome evolution has been developed that posits that sex chromosomes originate from an ordinary pair of autosomes harbouring a sex Cited by: accepted model of sex-chromosome evolution, in which homomorphic sex chromosomes progressively suppress recombination and become heteromorphic, predicts that the common ancestor of Ae. aegypti and An. gambiae had homomorphic sex chromosomes (Figure 1A). This implies that evolution of heteromorphic sex chromo-.
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  • Model of the evolution of sex chromosomes from a hermaphroditic state (40, 44). Evolutionary theory predicts that a nonre-combining genome is vulnerable to. Recently, empirical evidence has built on theoretical work and A common model of sex-chromosome evolution implies gradual Betran, E., Thornton, K. & Long, M. Retroposed new genes out of the X in Drosophila.
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