A phenotypically male patient with Kleinfelter syndrome with

A phenotypically male patient with Kleinfelter syndrome (with XXY chromosomes) is also afflicted with Norrie disease, a rare recessive mutation in a gene on the X chromosome that results in cataracts. The patient\'s mother (with XX chromosomes) and father (with XY chromosomes) are not afflicted with Norrie disease. Assuming no crossing over, what nondisjunction event resulted in Kleinfelter syndrome for this Norrie patient? Provide a scientific argument that best addresses this Question.

Solution

Norrie disease is an rare X-linked disorder that occurs due to errors or disruption mutations of the NDP gene due to mutations. Kleinfelter syndrome is a genetic condition that occur due to nondisjunction of chromosomes during meiosis. Due to error in cell division(nondisjunction), an egg or a sperm cell can carry an extra copy of X chromosome. And hence the embryo produced which develop into the baby will have extra copy of the X chromosome in each of their body\'s cells.

In the case in question, the patients mother might be a carrier for the norries disease gene. This diseased allele chromosome is carried to the egg due to nondisjunction and hence carries both the diseased alleles on X chromosome. One diseased allele transmits normally and other diseased allele transmits due to nondisjunction .Hence the patient might be afflicted with norries disease and kleinfelter syndrome both