Mongolism syndrome is caused by

Loss or gain of a segment of $DNA$ results in

Which one of the following is a type of hyperploidy?

Which one of the following conditions in humans is correctly matched with its chromosomal abnormality/linkage?

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?

What is the significance of Barr bodies and drumsticks to geneticists and biologists?