Question

Type 1 fucosidosis is a rare human disease. Patients cannot hydrolyze the disaccharide fucose, and as a result, they 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 and is inherited in an autosomal recessive manner. Jane and John have a child who has Type 1 fucosidosis. What is the probability that their next child will also have the disease?

O No chance
O 174
O 1/2
O 304
O 4/4 or 100%

Answer 1

The probability that Jane and John's next child will also have Type 1 fucosidosis is 25% since the disease is inherited in an autosomal recessive manner and both parents are carriers.

Step-by-step explanation:

Type 1 fucosidosis is an autosomal recessive disorder, which means that a child must inherit two defective genes (one from each parent) in order to exhibit the symptoms of the disease. Since Jane and John have a child who has Type 1 fucosidosis, we know that they are both carriers of the defective gene. For each child they have, there is a 1 in 4 chance, or 25% chance, that the child will inherit both defective genes and have the disease.

To understand the genetics behind this condition, we use a Punnett square. Both parents have one normal allele and one defective allele for the gene that codes for the enzyme that breaks down fucose. We represent the normal allele as 'F' and the defective allele as 'f'. The possible combinations for a child are 'FF' (normal), 'Ff' (carrier), 'fF' (carrier), and 'ff' (affected).

The probability that a child will inherit both defective alleles (ff) and have Type 1 fucosidosis is 25% because there is one 'ff' combination out of four possible combinations when the parents' alleles are combined.