1. Red-green colour blindness is sex linked. (Unless otherwise stated, ‘sex linked’ refers to a gene located on the non-homologous portion of the X chromosome.) The allele for red-green colour...
1. Red-green colour blindness is sex linked. (Unless otherwise stated, ‘sex linked’ refers to a gene located on the non-homologous portion of the X chromosome.) The allele for red-green colour blindness is recessive to the allele for normal vision. a)A normal sighted woman, whose father was red-green colour blind, married a man with normal vision. What ratios of genotypes and phenotypes would be expected among their children? b)Under what circumstances would all the daughters of a marriage have normal vision and all the sons be red-green colour blind?
1a. We can find the Genotypes of phenotypes of the children by using a Punett Square C:dominant gene for normal vision, c: recessive color-blindness, y: male gene w/o an allele for vision.
c Cc cy
C CC Cy
This tells us that 1/4 children will be color-blind and those will all be boys.
The other 1/2 of the boys will have normal vision from their mother. The girls will all have normal vision but 1/2 will be carriers of the gene.
1b. We can reverse engineer the Punett square to solve this one.
This leads us to
c Cc cy
c Cc cy
The Father has normal vision, and the mother is color blind. All the girls will inherit dad's normal vision, but the boys won't because it's not on the y-chromosome.