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Home Q & A Board Biology-Related Homework Help Genetics and Developmental Biology
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Courtney22132 Courtney22132
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10 years ago
The colour of eyes in fruit flies is determined by a gene on the X chromosome with two alleles.
XR= Red eyes. Xr= white eyes.
Cross a red eye male with a white eyed female. Show the genotypes and phenotypes, including the sex, of the parents and offspring…

Very lost on this one! It's for 5 marks and I'm a bit confused.
Thanks!
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10 years ago
Red eyed males are XR Y while white eyed females are Xr Xr. (If you don't understand why, just ask.)

Male offsprings will inherit a Y allele from "father" and a Xr from "mother". So all male offsprings are Xr Y, meaning they are all white eyed.

Female offsprings will inherit a XR from father and a Xr from mother, meaning they will all be red eyed. (XR Xr)

Crossing:
                      Male XR Y       female Xr Xr

Offsprings  XR Xr / Xr Y   (50% / 50%) (offsprings with Y are males)
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