A. Dominant alleles often encode functional products, whereas recessive alleles often do not encode functional products
Explanation:
One gene can have it's variant forms called allele but in one individual only two allele form of a gene can be present. These two allele form can be the same(homozygous) or different(heterozygous). A dominant allele often encode a function protein of product while recessive allele often code for non- functional product.
Therefore when the dominant allele is present in the chromosome then function products are formed which can be seen in the phenotype and even a single dominant allele produce the functional product like in heterozygous condition so phenotype in heterozygous and homozygous dominant condition appears same. So the correct answer is A.
