Which of the following karyotypes is diagnostic of Down syndrome
Explanation46,XX,der(14;21)(q10;q10)pat+21 indicates a female with an unbalanced Robertsonian translocation. 45,XX,rob,(14;21)(q10;q10) indicates a balanced carrier of a Robertsonian translocation. Note that it is now customary to use 'der' instead of 'rob' when describing the balanced carrier. and 253
