Mongolism syndrome is caused by

What is the sex chromosome complement in a male child with Down syndrome?

Three copies of chromosome-$21$ in a child with Down's syndrome have been analysed using molecular biology technology to detect any possible $DNA$ polymorphism with reference to different alleles located on chromosome-$21$. Results showed that out of $3$ copies,$2$ of the chromosomes of the child contain the same alleles as one of the mother's alleles. Based on this,when did the non-disjunction event most likely occur?

Which one of the following genetic disorders is $CORRECTLY$ matched with its karyotype?

Find the incorrect statement among the following:

An extra sex chromosome is present in . . . . . . .