The genotype is the phenotypes like code. Like, lets say jill had brown hair, her genotype is BB, since brown hair is a dominant trait, and lets say jill procreates with bill, and bill has blonde hair, his genotype may be bb. Their child would have either blonde hair or brown hair, but since jill has a dominant trait, their child's genotype would be Bb. One allele for brown hair and one allele for blonde hair. Same thing applies to diseases, eye color etc. The filled in circles are women with whatever the trait is. Lets say, affected by a cancer or diabetes. The filled in squares are the same, but for males. The non-filled in circles and squares either do not carry an allele at all and it will not display through them, or are carriers of the trait but will not display it, but may pass it on.
