How is autosomal recessive inheritance characterized?

How is autosomal recessive inheritance characterized?

• A. Only one parent's contribution determines the trait
• B. It requires one dominant and one recessive allele to express a trait
• C. Two copies of a recessive allele must be present to express the trait
• D. Only males can express the recessive traits

Answer: (C)

Autosomal recessive inheritance is characterized by the requirement of two copies of a recessive allele for the expression of a trait. This means that an individual must inherit one recessive allele from each parent to exhibit the associated phenotype. If a person has only one recessive allele and one dominant allele, the dominant allele will mask the effect of the recessive one, resulting in the dominant trait being expressed instead. This mode of inheritance is seen in various genetic disorders, such as cystic fibrosis and sickle cell anemia, where individuals who are carriers (those with one dominant and one recessive allele) do not display symptoms of the disorder but can pass the recessive allele to their offspring. For a child to express the autosomal recessive trait, both parents must either be affected or be carriers of the recessive allele, leading to a 25% chance with each offspring of being homozygous recessive, and thus expressing the trait. Consequently, the option that indicates the need for two copies of the recessive allele to express a trait accurately describes the fundamental principles of autosomal recessive inheritance.

Autosomal recessive inheritance is characterized by the requirement of two copies of a recessive allele for the expression of a trait. This means that an individual must inherit one recessive allele from each parent to exhibit the associated phenotype. If a person has only one recessive allele and one dominant allele, the dominant allele will mask the effect of the recessive one, resulting in the dominant trait being expressed instead.

This mode of inheritance is seen in various genetic disorders, such as cystic fibrosis and sickle cell anemia, where individuals who are carriers (those with one dominant and one recessive allele) do not display symptoms of the disorder but can pass the recessive allele to their offspring. For a child to express the autosomal recessive trait, both parents must either be affected or be carriers of the recessive allele, leading to a 25% chance with each offspring of being homozygous recessive, and thus expressing the trait.

Consequently, the option that indicates the need for two copies of the recessive allele to express a trait accurately describes the fundamental principles of autosomal recessive inheritance.