Sex chromosom history

These chromosomes would come to be known as the sex chromosomes, X and Y. The answer begins in the late s, when insect gonad cells, whose large chromosomes are easy to view through a microscope, were the specimen of choice for investigating the cellular basis of heredity. In , German biologist Hermann Henking counted 11 chromosomes in firebug Pyrrhocoris apterus sperm nuclei. McClung soon hypothesized that the accessory chromosome determined male sex.
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Sex chromosome

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sex chromosome | Definition, Examples, & Facts | Britannica

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. In mammals, birds, snakes and many lizards and fish, sex is determined genetically either male XY heterogamy or female ZW heterogamy , whereas in alligators, and in many reptiles and turtles, the temperature at which eggs are incubated determines sex. Evidently, different sex-determining systems and sex chromosome pairs have evolved independently in different vertebrate lineages.
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The evolution of the sex chromosomes: Step by step

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Metrics details. The recent sequencing of a large chunk of euchromatin from the human Y chromosome is a technical tour de force. It answers some evolutionary questions about this unusual chromosome while raising others.
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