D is the symbol for the dark-haired allele, d is the symbol for the blond-haired allele. Four children have the follwoing allele pairs: Lizzy has DD, Lena had Dd, Lyle had dD, and Laura has dd. Which child is considered recessive homozygous and has blond hair?

Explanation:

An homozygous organism has two similar alleles or the same recessive alleles. Humans usually inherits two variations of alleles, one from mother and the other from the father. However, recessive homozygous individuals have identitical alleles in their gene.

In this case, Laura is considered recessive homozygous and has blond hair because she has two blond-hair alleles symbolically 'dd' . If she had only one blond-hair allele, there would be only one 'd' allele in her gene with another allele.

However, she has two 'd' blond-hair allele which makes her recessive homozygous with a blond hair as 'd' allele is the symbol for the blond-haired allele.