The Barr body is observed in

Number of Barr bodies in $XXXXY$ is

The trisomic condition of $Down's$ syndrome arises due to:

When the chromosome number of a given organism has one additional chromosome in one of the homologous pairs,the condition is known as . . . . . .

Identify the disease on the basis of the following characters:
$(1)$ Short stature with a small round head.
$(2)$ Furrowed tongue and partially open mouth.
$(3)$ Palm is broad with a characteristic palm crease.

In Down's syndrome $(Mongolism)$,each cell has how many chromosomes?