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Sex determination in repriles

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Alex Quinn, a Ph. Sex-determining mechanisms in reptiles are broadly divided into two main categories: genotypic sex determination GSD and temperature-dependent sex determination TSD. Species in the genotypic group, like mammals and birds, have sex chromosomes, which in reptiles come in two major types. Many species—such as several species of turtle and lizards, like the green iguana—have X and Y sex chromosomes again, like mammals , with females being "homogametic," that is, having two identical X chromosomes. Males, on the other hand, are "heterogametic," with one X chromosome and one Y chromosome.
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Reptile sex determination goes wild

Sex determination in repriles
Sex determination in repriles
Sex determination in repriles
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Genes versus heat – a reptile sex trigger | New Scientist

In most animals the sex of an individual is determined at the moment of fertilization; when the egg and the sperm fuse together it is fixed if that animal will be male or female. Yet in many reptilian groups sex determination is established later during incubation, and the determinant external factor is the incubation temperature of the eggs. In reptiles, this means that the environment plays a crucial role in determining the sex ratio emerging from an egg clutch, and that these animals are very susceptible to alterations in temperature caused, for example, by climate change. In the majority of animal species, sexual differentiation the development of ovaries or testes is determined genetically GSD. In these cases, the sex of an individual is determined by a specific chromosome, gene or allele which will cause the differentiation to one sex or the other. In the case of reptiles, there is a great variety of sexual determination mechanisms. Still, in many groups the sex of the offspring is determined mainly by the egg incubation temperature TSD , and therefore the environment plays an important role in the proportion of males and females found in a population.
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Sex Determination in Reptiles

High temperatures can make an Australian lizard that is genetically male develop into a female. The finding throws new light on how sex is determined in reptiles. For most reptiles, a gene on a sex chromosome triggers an embryo to develop as either a male or a female. In some species, males have an X and a Y chromosome, while females are XX, as in mammals. In other species of lizards, males are ZZ while females are ZW, as in birds.
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Charles Darwin first provided a lucid explanation of how gender differences evolve nearly years ago. Yet, a disconnect remains between his theory of sexual selection and the mechanisms that underlie the development of males and females. In particular, comparisons between representatives of different phyla i. Such differences are hard to comprehend unless we study organisms that bridge the phylogenetic gap. Analysis of variation within monophyletic groups i.
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