Question

Spinal muscular atrophy is a recessive disorder described as autosomal. On the basis of this knowledge, what is the percentage of possibility that if a child's parents are carriers of the disorder, the child won't have a recessive allele?

A. 50%
B. 0%
C. 25%
D. 100%

Answer 1

In the case of a recessive disorder described as autosomal, if both parents are carriers of the disorder, there is a 25% possibility that the child won't have a recessive allele.

Step-by-step explanation:

In the case of a recessive disorder described as autosomal, if both parents are carriers of the disorder, there is a 25% possibility that the child won't have a recessive allele.

Let's use an example to understand this better. Let's say the parents have the genotype Aa, where 'A' represents the dominant allele (normal) and 'a' represents the recessive allele (carrier). When they have a child, there are four possible combinations of alleles: AA, Aa, aA, and aa. Only one of these combinations (AA) does not have a recessive allele, while the other three combinations (Aa, aA, and aa) have at least one recessive allele.

Therefore, the child has a 25% chance of not having a recessive allele, which means there is a 75% chance of having a recessive allele.