Question

What is the genotype of individual B in generation I?

Answer 1

We have to consider that female individuals are represented by a circle, while males with a square. When these forms are shaded, what's indicated, is that they express a particular trait of consideration, which usually is genotypically represented by two recessive alleles in females, and only one in males (due to the corresponding inherited chromosomes: males have only one X chromosome, while women have two of them).

In this case, then, the genotype of the individual B in the first generation is XBXb, since only with this female genotype, the given offspring is reached.

In the Punnet square, we can see how with the mother's genotype being XBXb, there's an offspring like the exercise tell us, being green circles and squares. the healthy ones, and red circles and squares the one that has the disease.