What is the ratio in this dihybrid cross?

.DIHYBRID CROSS.
Heterozygous organism - RrYy
Homozygous recessive organism - rryy

A dihybrid cross gives you
___RY ___ Ry ___ rY ___ ry
________________________
ry | RrYy..| Rryy.. | rrYy ...| rryy.. |
________________________
ry | RrYy..| Rryy.. | rrYy ...| rryy.. |
________________________
ry | RrYy..| Rryy.. | rrYy ...| rryy.. |
________________________
ry | RrYy..| Rryy.. | rrYy ...| rryy.. |
________________________

You get (4 : 4 : 4 :4) in genotypic as well as phenotypic ratio
Resolving this you get,

Genotypic ratio = 1 :1: 1: 1
Phenotypic ratio = 1 : 1 :1 :1

That's not a complete question.

Do you mean that one organism is heterozygous for BOTH characters, and the other organism is homozygous recessive for BOTH characters?  If so, you need to state that.




Assuming that above is the case, here is a monohybrid cross between them for one character.

........A....a
.....-----------
a...|.Aa...aa
a...|.Aa...aa

Aa = 50% (frequency is for both genotype and phenotype)
aa = 50% (frequency is for both genotype and phenotype)


We would get the same results for the second monohybrid cross, just using a different letter (B and b).

Now we combine the results from the two monohybrid crosses to get the results for a dihybrid cross.

AaBb = 50% x 50% = 25% (frequency for both genotype and phenotype)
Aabb = 50% x 50% = 25% (frequency for both genotype and phenotype)
aaBb = 50% x 50% = 25% (frequency for both genotype and phenotype)
aabb = 50% x 50% = 25% (frequency for both genotype and phenotype)


So the ratio between the genotypes, as well as for the phenotypes, is 1:1:1:1.