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Chromosomes

Two normal parents have 3 children, one a normal girl, one a normal boy and the other boy with hemophilia. If the affected son marries a girl whose father also had hemophilia, what are the overall chances of having a hemophiliac child?

A male from India carries an odd trait for hairy ears that is based on the Y chromosome. Assuming he mates with a woman whose father carries that trait, what percentage of daughters will have or carry the trait? What percentage of sons will have or car5ry the trait?

A group of traits is being studied for their effects on behavior by researchers. There are 10 total traits being studied. If this combination is as shown below (assuming no linkage), how many different gamete combinations are possible? What are they?
AA Bb CC DD EE Ef GG HH Ii JJ

Solution Preview

Two normal parents have 3 children, one a normal girl, one a normal boy and the other boy with hemophilia. If the affected son marries a girl whose father also had hemophilia, what are the overall chances of having a hemophiliac child?

Hemophilia is an x-linked gene recessive gene. Therefore, the affected son is X^hY where "^h" means "superscript h." What about his wife? We know that her father was a hemophiliac. Therefore, her father was X^hY. That means that she must have gotten the X^h chromosome from her father and another (normal) X chromosome from her mother. Therefore, she is X^hX. Therefore, she's a carrier.

Now, we do the Punnett Square.

X^h Y
X^h X^hX^h X^hY
X ...

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