In Klinefelter's syndrome,what is generally the set of sex chromosomes?

The Mongoloid condition is related to,or in mongolism,a patient shows:

In humans,sometimes during gametogenesis,sex chromosomes do not separate,resulting in a chromosome number of $45$,$47$,or $48$. In this condition,which of the following genotype and phenotype combinations is correct?

Who reported that Down's syndrome is due to an extra $21^{st}$ chromosome?

Which event in the chromosomal structure leads to the formation of a syndrome?

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