S.V.T. terminale D - Biologie Hérédité et Génétique

Hérédité liée au sexe (html)

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Sex-Linked Inheritance: Drosophila

Legend:
Drosophila are used to illustrate how alleles on sex chromosomes are inherited in predictable patterns.

In sex-linked inheritance, alleles on sex chromosomes are inherited in predictable patterns.
For example, in Drosophila the locus for eye color is located on the X chromosome.
The allele for red eye color, which is normal in wild flies, is dominant to the mutant allele for white eyes.

As females have two chromosomes X (with a locus for eye color), they might be homozygous or heterozygous for either allele.

Males, who carry only one X chromosome, are always hemizygous. They carry only the one X chromosome inherited from their mother, and it determines their eye color.

In the left hand example, homozygous red eyed females (RR) mate with hemizygous white eyed males (w-). In the offspring, all the daughters are red eyed heterozygotes (Rw) and all sons are red eyed hemizygotes (R-).

In the right hand, homozygous white eyed females (ww) mate with hemizygous red eyed males (R-).

In the offspring, all the daughters are red eyed heterozygotes (Rw) and all sons are white eyed hemizygotes (w-).

 


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