To determine the genotype of the parents and their children, we can use a Punnett square. We know that the daughter is colorblind, which means that she has two X chromosomes with the colorblind allele. The son has normal vision, which means that he has at least one X chromosome with the normal vision allele.
Let's use "C" to represent the normal vision allele and "c" to represent the colorblind allele.
The father's genotype could be CC or Cc, and the mother's genotype could be CC, Cc, or cc. We don't know their genotypes for sure, but we can create a Punnett square to show the possible outcomes for their children:
| C | c
--|----|----
C | CC | Cc
--|----|----
C | CC | Cc
--|----|----
c | Cc | cc
In this Punnett square, we see that there is a 50% chance that each child will receive a colorblind allele from the mother. The daughter received two copies of the colorblind allele (cc), while the son received one copy of the normal vision allele and one copy of the colorblind allele (Cc). This explains why the daughter is colorblind and the son has normal vision.
So, the doctor could conclude that the daughter is homozygous recessive for the colorblind allele (cc), and the son is heterozygous (Cc) for the colorblind allele.