Genetics of Colour Blindness: A Familial Inheritance Question

[rapidfire5]

ok i have this question for homework, can anyone help me?

A man's maternal grandmother had normal vision; his maternal grandfather was colour-blind;his mother is colour-blined;his father has normal vision. Calculate the genotypes of the two parents and grandparents mentioned? What type of vision has this man himself? His sister?

Thanks xD

 

[iansmith]

You have to show us that have tried to solve the problem before we can help you.

Here a few questions to get you started:
Is colour blindness dominant or recessive, is heredity linked to any specific trait?
Can you do a punnet square for the maternal grandparent and the mother?

 

[rapidfire5]

You have to show us that have tried to solve the problem before we can help you.

Here a few questions to get you started:
Is colour blindness dominant or recessive, is heredity linked to any specific trait?
Can you do a punnet square for the maternal grandparent and the mother?

yea we use dat punnet square

 

[iansmith]

Do you know if color-blind is a recessive or dominant trait and if it is linked to any other trait (i.e. the sex/X and Y chromosome)?

this information is crucial for the punnet square.

 

[rapidfire5]

this is how i did it, its starts at question 2

 

[iansmith]

Colour blindness is a recessive trait and therefore a female colour blind must be homozygous recessive and have both X^rX^r. A normal woman will be either homozygous dominant or heterozygous (X^RX^R or X^RX^r)

Furthermore the gene is absent on the Y chromosome. So a colour blind man is X^rY and a normal individual is X^RY

You may want to redo the problem.