Question

What is the mode of inheritance for the trait fragile X syndrome?
A. X linked recessive
B. X linked dominant
C. Autosomal recessive
D. Autosomal dominant

Answer 1

Hint:
Fragile X syndrome is a genetic condition associated with cognitive impairments and learning disabilities. Speech and language development are usually delayed by the age of two in affected individuals Fidgeting and hyperactivity are also common characteristics of children with fragile X syndrome. There might be an attention deficit disorder (ADD), which is characterized by difficulty focusing on a particular task and an inability to maintain attention.

Complete step by step answer:
 "X-linked recessive inheritance" is a type of inheritance where a gene on the X chromosome undergoes mutation, which results in the expression of a phenotype in males and females who are homozygous for the mutation. Autosomal dominant traits pass from one of the parents onto their child, and autosomal recessive traits pass from both parents onto their child.
An X-linked condition is caused by a mutated gene on one of the two sex chromosomes, the X chromosome. Dominant inheritance is when only one copy of an altered gene can cause the condition in each cell. Females (who have two X chromosomes) are prone to an X-linked dominant disorder because mutations occur in a single copy among the double copies of a gene in a cell. In males, if the mutation occurs in a single copy of the gene, it causes the disorder. Fragile X syndrome is a condition inherited in an X-linked dominant pattern. This disease occurs as a result of a mutation in the FMR1 gene on the X-chromosomes.

Option ‘B’ is correct

Note:
The mutation on the FMR1 gene prevents the gene from properly making fragile X mental retardation-1 protein, which plays a role in the functioning of the nervous system. A shortage of this protein results in the symptoms of FXS.