Under what condition will an offspring express an autosomal recessive condition?

Under what condition will an offspring express an autosomal recessive condition?

• A. It has the dominant gene for that condition.
• B. It is heterozygous for the gene that causes the condition.
• C. It is homozygous for the gene that causes the condition.
• D. It has inherited the recessive genes from its mother.

Answer: (C)

For an offspring to express an autosomal recessive condition, it must be homozygous for the recessive allele associated with that condition. This means the offspring must inherit two copies of the recessive gene—one from each parent. The presence of one dominant allele is sufficient to mask the expression of the recessive allele, resulting in the dominant phenotype. Therefore, only when an individual possesses two recessive alleles does the autosomal recessive condition manifest itself. This understanding is critical when analyzing genetic inheritance patterns, as it highlights the importance of both parental contributions. For example, if both parents are carriers of the recessive allele (heterozygous), there is a chance, typically 25%, that the offspring could inherit the recessive allele from both parents, thereby expressing the autosomal recessive condition.

For an offspring to express an autosomal recessive condition, it must be homozygous for the recessive allele associated with that condition. This means the offspring must inherit two copies of the recessive gene—one from each parent. The presence of one dominant allele is sufficient to mask the expression of the recessive allele, resulting in the dominant phenotype. Therefore, only when an individual possesses two recessive alleles does the autosomal recessive condition manifest itself.

This understanding is critical when analyzing genetic inheritance patterns, as it highlights the importance of both parental contributions. For example, if both parents are carriers of the recessive allele (heterozygous), there is a chance, typically 25%, that the offspring could inherit the recessive allele from both parents, thereby expressing the autosomal recessive condition.