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Sex-Linkage (X-Linked Traits)

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Presentation on theme: "Sex-Linkage (X-Linked Traits)"— Presentation transcript:

1 Sex-Linkage (X-Linked Traits)
Drosophila melanogaster

2 Thomas Hunt Morgan – (the father of modern genetics)
He found genes located on the X chromosome that regulate fruit fly eye color. Genes on the X chromosome are said to be X-linked

3 Thomas Hunt Morgan was studying evolution and was looking for mutations in fruit flies (Drosophila).
Morgan and his “F1s” (His two daughters)

4 Morgan noticed that while most fruit flies had red eyes, there were a few white-eyed fruit flies.
He also noticed that ones that had white eyes were all males.

5 Morgan’s Experiment: 1) Morgan crossed a true-breeding, red-eyed female with a white-eyed male, he got all red-eyed flies in the F1 generation.

6 WHY? 2) When he crossed two F1 red-eyed flies,
he got three red-eyed flies to every one white-eyed fly. ALSO-the white-eyed flies were male. WHY?

7 As stated by Morgan the gene for eye color is located on the X chromosome.
R = red color r = …white complelely color dominant over the…





12 more often than females
Male fruit flies have white eyes more often than females Because females get a second chance at a dominant gene, they’re usually red-eyed. Males only get one chance at a dominant. Males are more likely to express recessive traits if the gene is on the X chromosome. (hemophilia, color-blindness, muscular dystrophy.)

13 Other interesting Drosophila variations:

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