Incomplete dominance, sex-linked and Dihybrid crosses

[msfancy]

Hi there, im doing some assignment questions and need a little help anwsering this question.

1) Diagram the following crosses and state expected phenotype ratios:

A color-bline man mates with a woman who is a carrier for the recessive color-blind allele.

- msfancy

[domwood]

This would be the sex-linked part of the title, colour blindnesses is an X linked disease.

The cross is X"Y with X"X (X' is the X chromosome with the colour blind allele)
So you just need to get do a crossing table to work out the four possible genotypes.

Also When working out the phenotype remember that:
Men are XY, so only have one x chromosome.
So even if the disease is recessive, you can consider it pseudo-dominant for men as if they have the allele they will always have the disease.

I hope this helps.

[msfancy]

Thank you so much it helped out alot. And makes a lot more sence to me now.

[msfancy]

--- Two Brown labrador retrievers are crossed. The trait shows incomple dominance with Brown being the color of the hybrids. The other variations of the phenotype are yellow and Black.

Im trying to figure out if this means that the labs are Brown-yellow, and Brown-black? Brown being dominate and yellow and black the recessive.

[MrMistery]

look up how incomplete dominance works. There is no allele for brown.