I know how to do tests crosses for genes but don't understand how to calculate the pheonotype or genotype ratios. So can you guys do a dihybrid cross, crossing RRYY with rryy and then tell me what the phenotype and genotype ratios are and how you got them?

http://en.wikipedia.org/wiki/Punnett_square

RRYY and rryy yields a 4x4 square. Fill it correctly and check for all genotypes. Then by considering dominant and recessive alleles, determine the phenotypes (you should have 4 different ones). Then just calculate the ratios a:b:c:d