Normal sighted man has children with normal sighted woman?

Question

They have 2 daughters who have normal vision, but one of their 2 sons is colour blind.

What is happening in this cross?

The colour blind son then went on to have children with a normal sighted women and have a daughter who is colour blind.

What is happening in this cross?

Answer 1

Color blindness is a recessive gene, so if you have a normal vision gene and a color blind gene, you will have normal vision because that is the dominant gene.
But if you had 2 recessive color blind genes (one from each parent) you will be color blind.
So, obviously each parent had one dominant and one recessive gene for color blindness and they both passed on the recessive gene to the boy that is color blind.

Then that boy (who can only pass on the recessive color blind genebecause that's all he has) mated with a normal visioned woman who has one dominant gene and the recessive gene and they both passed the recessive gene to the daughter.

Answer 2

Colour-blindness gene is carried on the X chromosome - mother has 2, father has only 1.

Genotypes: mother +cb father +-

mother gametes + (normal) or cb; father +

Offspring - daughters either ++ or cb+, both have normal vision.

Son cb - therefore colour blind.

Next cross man cb- x +cb

daughter cb cb has inherited colour-blind allele from both parents, therefore mother was a carrier.

It is a characteristic of sex-linked traits (i.e. those carried on the X chromosome, that they are expressed in the opposite sex each generation. A female carrier can produce and affected son by passing the affected X. Father has no effect as he gives a Y to his son. An affected male can only produce an affected daughter rather than son as he passed on the affected X chromosome. Of course if an affected male is crossed with a normal female then the daughter will be a carrier.

Answer 3

Colour blindness is a recessive Gene, however, it is X-linked therefore any male with the gene will be colour-blind. Women are more often carriers but not actually colour blind themselves

For a woman to be colour-blind, her father must be colour-blind and her mother must be a carrier.

Colour-blind females are extremely rare, just like female haemophiliacs which is also an X-linked condition.

Answer 4

The answers about the genes are correct - colour-blindness is carried on the X chromosome. I can't help feeling that you were asking because you got suddenly concerned about a related (!) issue, but you have no reason to be worried on the basis of colour-blindedness.

Answer 5

The man has an x chromosome normal vision the woman has one x chromosome for normal vision and one for color blindness (recessive). The son gets one x chromosome from his mother for color blindness but gets a y chromosome from his father. He married a woman with one x chromosome for normal vision and one for color blindness (recessive). His daughter gets x genes for color blindness from her mother and her father

Answer 6

Are you cousins from Kentucky? That could explain some things!

Answer 7

mistress would be correct..

look up punnet squares they will help have a better understanding of this

http://www.athro.com/evo/gen/punexam.html

Answer 8

it might be from years previous