Which of the following statements about recessive alleles is true?

The statement that recessive alleles typically produce less functional protein than normal alleles is accurate. Recessive alleles can lead to a phenotype that only manifests when an individual carries two copies of the recessive allele, meaning that the effects of the dominant allele can overshadow them in a heterozygous individual.

In many cases, recessive alleles result from mutations that lead to a loss of function in the protein they encode. This could mean that the recessive allele produces a non-functional protein or, in some cases, a protein that is less effective than the protein produced by the dominant allele. Therefore, when an organism has two recessive alleles, there's an absence or decrease in the amount of functional protein, which can significantly affect the phenotype.

The other statements do not accurately reflect the nature of recessive alleles. While recessive alleles may not usually contribute to phenotypes when a dominant allele is present, they do not inherently mask dominant alleles; instead, they are masked by them. Recessive alleles can sometimes manifest phenotypically if the individual is homozygous recessive, but their role is typically less dominant in terms of phenotype expression compared to dominant alleles.