44. When a person has Down syndrome, he or she has an extra chromosome 21. Therefore, Down syndrome is a kind of _____ and results from _____.
a. aneuploidy ... nondisjunction of chromosome 21 during meiosis I
b. polyploidy ... occurrence of meiosis without cytokinesis
c. genomic imprint ... excessive methylation of either the paternal or maternal chromosome 21
d. replication error ... an extra cycle of DNA synthesis during the S phase
e. none of the above

Question

44.	When a person has Down syndrome, he or she has an extra chromosome 21. Therefore, Down syndrome is a kind of _____ and results from _____.  
a.	aneuploidy ... nondisjunction of chromosome 21 during meiosis I
b.	polyploidy ... occurrence of meiosis without cytokinesis
c.	genomic imprint ... excessive methylation of either the paternal or maternal chromosome 21
d.	replication error ... an extra cycle of DNA synthesis during the S phase
e.	none of the above

alphadxg · Answer

It will be A, you don't really need to know the definition but if you know nondisjunction adds + and - of chromosomes in certain haploid cells,

more about this I also have for you here: Aneuploidy is a condition in which the chromosome number is not an exact multiple of the number characteristic of a particular species. An extra or missing chromosome is a common cause of genetic disorders including human birth defects. Some cancer cells also have abnormal numbers of chromosomes.[1] Aneuploidy originates during cell division when the chromosomes do not separate properly between the two cells. This generally happens when cytokinesis begins while karyokinesis is still under way.