Question

The disease called branched-chain ketoaciduria is commonly known as maple syrup urine disease, as the urine of a person with the condition has a smell similar to that of maple syrup. Because the disease is rare and most often appears in children whose parents are first cousins, one can conclude that the disease is inherited as an autosomal _______ phenotype.

Answer 1

Answer:

Recessive

Explanation:

A recessive disorder is expressed in a homozygous genotype only. Most of the recessive disorders are not expressed as the expression of the recessive allele is masked by a dominant allele in the heterozygous state. However, breeding between close relative (inbreeding) increases the homozygosity in the population and allows the expression of recessive alleles that were otherwise not expressed in the population.

According to the given information, the disease is rare and is mostly expressed in the progeny obtained by mating between closely related individuals (the first cousins). Therefore the disease is inherited in an autosomal recessive pattern.