Question

Which of the following IS NOT a balanced carrier of a chromosome rearrangement?

	A.	An individual with karyotype 45,XX, t(14q /21q)
	B.	An individual with karyotype 46,XX, t (14q/21q)
	C.	A mentally retarded child with deletion of the last two bands of the ‘p’ arm in one of the copies of chromosome 5
	D.	A normal 40-year old woman with 46 chromosomes who has a reciprocal translocation between chromosomes 18 and 20
	E.	A phenotypically normal woman with an autosomal inversion who has a history of a miscarriage.
	F.	Two of the above
	G.	Three of the above

Answer 1

A mentally retarded child with deletion of the last two bands of the ‘p’ arm in one of the copies of chromosome 5 - This deletion leads to Cri du chat syndrome. It is caused due to the inheritance of unbalanced translocation from a parent, where the short arm of the chromosome 5 is missing.

Both Robertsonian translocations are balanced, autosomal inversions are always balanced and the the normal woman with reciprocal translocation will be a carrier of balanced reciprocal translocation.