Question

As an optician, you help to diagnose many common eyedisorders, such as nearsightedness and glaucoma. Currentlyin your office is Gabriel, a young boy who you just diagnosedas having red-green colorblindness. His parents, Catalina andRobert, seem surprised by this diagnosis, as neither of themis colorblind. They have many questions aboutcolorblindness. Using your knowledge of human genetics, youdo your best to answer their questions.

Answer 1

We can indicate the allele for colorblindness with lowercase b, and the allele for normal vision with a capital B. None of Gabriel's parents have the disease, but her mother is a carrier. This can be expressed as follows:

Gabriel's father

BB

Gabriel's mother

Bb

Another consideration that's needed to be done, is that this is an X chromosome-linked condition. We also know that XX is the chromosomes inherited by females, and XY the chromosomes inherited by males.

Having considered this, we can say that Gabriel's parents would have the following genotypes:

Gabriel's father

XBY

Gabriel's mother

XBXb

We have then this Punnet Square:

Upon this, we can say that there's an odd of 25 % of having a son with the disease, while a 75 % of having a healthy offspring (25 % of having a carrier daughter, and 50 % of having healthy-non carriers children).

So the correct statements of the question are the first one, the second one, and the final one.