Fragile x syndrome, characterized by mental r. e.t. a.r. d.a. t.i. o.n (spaced oot because filter), is caused by which chromosomal change?
a) deletion
b) translocation
c) inversion
d) insertion

Ans.

Fragile X syndrome is defined as a genetic disease, results in cognitive impairment and mental problems.

It is caused by a mutation in FMR1 gene that causes an increase in the CGG trinucleotide units in the gene. This is an example of insertion mutation as it involves addition of nucleotide sequences to the gene.

The FMR1 gene codes for a protein, which is necessary for normal cognitive functions and defect in this protein, due to mutated gene leads to development of disorder.

Thus, the correct answer is option D). 'insertion.'

a motor homunculus represents a map of brain areas dedicated to motor processing for different anatomical divisions of the body.

homunculus represents the importance of various parts of your body as seen by your brain. as a result, they take up a lot of brain space. although the cortical homunculus is a curiosity, penfield's work in mapping the brain's relationship to the body was invaluable.