I'm reading through some science that could come up in my GRE equivalency.
I've never been much of a biologist, more of a chemist/geologist....though it does interest me massively!
I'm just seeing this question in a textbook....
Q) Assume eye colour in humans is controlled by a pair of alleles of a gene where the allele giving brown eyes is dominant to the allele giving blue eyes. Both parents of a blue eyed man, John, were brown eyed. He married a brown eyed woman, Sara, whose father had brown eyes and mother blue eyes. Sara had a blue eyed sister. John and Sara had a brown eyed child.
Fill in the boxes and circles on the family tree below to show the genotype of each individual.
I just wanted to ask how exactly we mark out genotype in science? Do we use D's and r's?