Autosomal recessive inheritance typically requires what for the disease to manifest?

• A. One copy of the gene
• B. Two copies of the gene
• C. No copies of the gene
• D. Three copies of the gene

Answer: (B)

In autosomal recessive inheritance, a disease or trait manifests only when an individual has two copies of the recessive allele for a specific gene. This means that both alleles inherited from each parent must be the recessive variant for the individual to express the associated phenotype. An individual with just one recessive allele and one dominant allele will not exhibit the disease; instead, they will be a carrier of the recessive trait. This is a fundamental principle of genetics, highlighting the importance of allele interactions in determining the expression of traits. Only when both alleles are recessive does the associated characteristic or condition present itself in the phenotype.