A full-term female newborn is examined shortly after birth. She appears to be small for gestational age, and she has excess skin on the nape of the neck and lymphedema of the hands and feet. Chromosomal analysis shows some cells with a normal 46,XY karyotype and some cells with a 45,X karyotype. Which of the following mechanisms best explains this cytogenetic abnormality?
A. Nondisjunction in mitosis
B. Reciprocal translocation
C. Robertsonian translocation
D. Skewed X-inactivation
E. Uniparental disomy
Correct answer : A. Nondisjunction in mitosis
This is a case of mosaic turner syndrome due to nondisjunction of chromosomes.