Down syndrome is a common disorder.Which of the following circumstances results in Down syndrome?

A) Defective,recessive alleles
B) Defective,dominant alleles
C) Insufficient number of chromosomes
D) Extra chromosome

Down Syndrome

A genetic disorder caused by the presence of all or part of a third copy of chromosome 21, resulting in a distinctive set of physical and intellectual traits.

Extra Chromosome

A genetic condition where an individual has more than the usual number of chromosomes, leading to developmental differences and physical anomalies.