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9 years ago
A woman is color-blind. Her husband has normal color vision. (Color vision is dominant over color-blindness) They have 12 children. All daughters have normal color vision while all sons are color blind. Do these offspring indicate that color-blindness is sex-linked or that it is not sex-linked?  I don't get this please answer and explain?  Face with Open Mouth Face with Open Mouth Confounded Face Crying Face
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Educator
9 years ago
Colorblindedness is on the X chromosome
lets say normal = X
colorblind = X*

as color vision is dominant that means the woman has to be homozygous recessive or X*X* ( because if she had one normal X then she could see color)

Males cant be "carriers" because they only get one X and so if the man has normal vision he has to be XY
( colorblind males are X*Y)

the punnet would look like this

..... X* X*

..... X XX* XX*

..... Y X*Y X*Y

that result means that all the girls will see color but are carriers

and all the sons are colorblind

it is therefore indeed sex-linked

If it were not linked to the X then there would be normal vision males who are also carriers ( they would have equal chance of getting the gene from their Mom or Dad but if it werent sex linked it wouldnt be definite--only when it is "linked" or attached to either the y or x chromosome does this pattern occur.)
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