Tortoiseshell cats almost all female because the genes coding for fur colour are on the X chromosomes - the black fur gene on one and the orange one on the other. In each cell, only one X chromosome is activated, giving a patchwork pattern.
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Watch the full first lecture of the series: https://www.rigb.org/christmas-lectures/watch/1984/the-message-of-the-genes/we-are-all-different?utm_source=youtube&utm_medium=social&utm_term=description
Walter Bodmer gave the 1984 Christmas Lectures "The Message of the Genes" about how much of the variety of mankind can be explained by genetics.
The first lecture where this clip is from is about the differences between humans, and what makes us individuals.
Watch the full series: https://www.rigb.org/christmas-lectures/watch/1984/the-message-of-the-genes?utm_source=youtube&utm_medium=social&utm_term=description
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