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.
sex chromosome | Definition, Examples, & Facts | Britannica
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.