Euploidy is best explained by

Absence or excess or abnormal arrangement of one or more chromosomes results in

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?

In man,which of the following genotypes and phenotypes may be the correct result of aneuploidy in sex chromosomes?

Mark the odd one with respect to the syndrome which occurs due to the failure of segregation of homologous pairs of chromosomes during the cell division cycle.

The loss of a chromosomal segment is due to