<span>The connective tissue membranes that are found lining the joint cavities are called the synovial membranes. Joint cavities, like the shoulders, elbows, or knees, are known as freely movable joints. The synovial membranes line joint cavities that are not open to the outside.</span>
Ans.
HD (Huntington's disease) is a genetic neurological disorder that occurs due to damage and death of brain cells. it is caused by an autosomal dominant mutation in HTT (huntingtin) gene, having a trinucleotide repeat section that makes HTT protein.
The mutation leads to an increase in this nucleotide repeat count, associated with formation of altered or mutated huntingtin protein. These altered proteins show deleterious affect on brain cells and result in Huntington's disease.
Thus, the correct answer is 'option A). a mutated gene.'
