Human recessive alleles are often caused by mutations that result in a loss of function in which enzyme?

• A. Translated
• B. Coded
• C. Produced
• D. Activated

Answer: (B)

The correct answer pertains to the concept of how recessive alleles often arise from mutations. In general, recessive alleles are typically the result of mutations that lead to a loss of function of proteins or enzymes that are crucial for normal cellular processes.

When we say that these mutations result in loss of function, we refer to the protein or enzyme being coded by the gene. A recessive allele means that two copies of the mutated gene are usually necessary for a phenotype to be expressed. If only one copy is present, the functional allele can often compensate, thus masking the effect of the recessive allele.

In this context, the term "coded" is appropriate because it directly relates to the genetic code – the sequence of nucleotides in DNA that determines what protein is produced. The mutations in recessive alleles disrupt this coding, ultimately leading to a nonfunctional or improperly functioning enzyme. Therefore, identifying recessive alleles with mutations resulting in a loss of function highlights the central role of the genetic coding in determining phenotypic traits.