X-linked Dominant

Question 1

Fragile X syndrome

Answer 1

Onset at childhood, mental deficiency, dysmorphic facies, male postpubertal macroorchidism (enlarged testicles); speech/language delay, autism-like syndromes, large ears/prominent jaws
Fragile X-associated tremor/ataxia syndrome (FXTAS): from premutation, Parkinsonian-like features, adult onset, ataxia, tremor, memory loss, peripheral neuropathy
Premature Ovarian failure in women (20% of women with permutation)

Trinucleotide CGG expansion (>200 penetrant, 6-45 normal, grey zone/premutation in between) in 5’ UTR causing hypermethylation, and thus silencing of gene at fragile site of X chromosome
Maternal gene anticipation
Premutation is 59