Question

Pedigrees are used to help geneticists understand how traits are inherited between generations. The Romanovs, a Russian royal family, had a history of hemophilia, a sex-linked disorder that is determined by a recessive allele on the X chromosome.

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What is the best evidence to prove that Irene was heterozygous for hemophilia?
Alice carried the recessive allele.
Alexandra carried the recessive allele.
Frederick carried the recessive allele.
Waldemar carried the recessive allele.

Answer 1

The answer is A, Alice.

Answer 2

A. Alice carried the recessive allele

Step-by-step explanation

A daughter receives an X chromosome from the mother and an X chromosome from her father. If the X chromosome from the mother has the gene for normal blood clotting and that X chromosome from the father has the gene for hemophilia, the daughter will be a carrier for hemophilia because the normal blood clotting gene from the mother is dominant.