Being able to roll your tongue is dominant to not being able to roll your tongue. smooth middle knuckles are dominant to hairy middle knuckles. predict the outcome between two people that are heterozygous for both traits

9 tongue roller and smooth middle knuckles: 3 tongue roller and hairy middle knuckles : 3 Non-roller and smooth middle knuckle: 1 non-roller and hairy middle knuckle.  

Explanation:

Let's assume that allele for tongue roll is "R" and the allele for the non-roller phenotype is "r". Similarly, allele "S" determines smooth middle knuckles while its recessive counterpart "s" gives hairy middle knuckles.  

The genotype of heterozygous parents would be "RrSs" and a cross between two "RrSs" genotypes would give progeny in the following phenotype ratio=

9 tongue roller and smooth middle knuckles: 3 tongue roller and hairy middle knuckles : 3 Non-roller and smooth middle knuckle: 1 non-roller and hairy middle knuckle.  

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