Question

Type 1 fucosidosis is a rare human disease. Patients cannot hydrolyze the disaccharide fucose, and as a result have severe neurological decline and die by age 6. The disease is due to a defect in the gene that encodes the lysosomal enzyme that breaks down fucose (α-1-fucosidase), and is inherited in an autosomal recessive manner. Which of the following statements is ACCURATE about Type1 fucosidosis?

A. Ff and ff individuals will have the disease
B. Ff individuals will have the disease, because anyone with the mutant allele will have the disease
C. Ff individuals make enough α-1-fucosidase to break down fucose and do not exhibit the condition
D. Two carriers for Type I fucosidosis have no chance of having a normal child
E. Both Ff individuals will have the disease, because anyone with the mutant allele will have the disease AND two carriers for Type I fucosidosis have no chance of having a normal child

Answer 1

The correct statement about Type 1 fucosidosis is that (C) Ff individuals produce enough of the enzyme α-1-fucosidase to prevent the disease, because having one functioning allele is sufficient. Two carriers have a 25% chance of having a child with the condition.

Step-by-step explanation:

Type 1 fucosidosis is a rare human disease caused by a genetic defect in the enzyme α-1-fucosidase which is crucial for the breakdown of fucose. This disease is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the defective gene, one from each parent, to exhibit the condition.

The correct statement about Type 1 fucosidosis is that C. Ff individuals make enough α-1-fucosidase to break down fucose and do not exhibit the condition. This is because the presence of one functioning allele (F) produces sufficient enzyme to prevent the symptoms of the disease. These Ff individuals are carriers of the disease but do not show signs of it. If two carriers (Ff) have a child, there is a 25% chance that the child will inherit two defective genes (ff), a 50% chance that the child will also be a carrier (Ff), and a 25% chance of the child inheriting normal genes (FF).