Question 64126

Certain dominant alleles are so important for normal development that the mutant recessive alleles, when homozygous, lead to the death of the organism. However, such recessive alleles can be perpetuated as heterozygotes (Ll), which in many cases are not phenotypically different from homozygous (LL) normals. Consider the matting of two such heterozygotes, Ll x Ll. among their surviving progeny, what is the probability that an individual will be heterozygous?