Brown eyes are a dominant eye-color allele and blue eyes are recessive. A brown-eyed woman whose father had blue eyes and whose mother had brown eyes marries a brown-eyed man whose parents are also brown-eyed. They have a son who is blue-eyed. Please draw…
Squares indicate MALES
Circles indicate FEMALES
The genotypes of the man’s parents and woman’s mother are inconclusive.
Every other genotype is certain.
Okay so blue eyes (b) is the recessive allele, meaning it needs two copies in order to show up in the phenotype.
Brown eyes (B) are dominant alleles, and only one copy is sufficient for it to appear in the phenotype.
If the son has blue eyes, it means he has no B alleles and only b alleles.
The son receive one allele from his mum, the other from his dad.
So obviously both parents EACH has a b allele.
But both parents had brown eyes, so they must have had a B allele too.
The mother’s father has blue eyes, hence he must have two b alleles.
The alleles of the other cannot be decided through the information given