Question

Which effect is most likely caused by nondisjunction during meiosis?

Answer 1

The answer to the question would be an extra chromosome.

Meiosis is a type of cell division which all sexually reproducing diploid eukaryotes have. It is finished in the process of fertilization, resulting in a zygote. The chromosome number is divided by half in this process, resulting in four haploid cells which all differ genetically from the parent cells. After DNA replication, two cell divisions take place, referred to as Meiosis I and Meiosis II. The first cell division generates the diversity of genetic information through the process of crossing over and random positioning of homologous chromosomes. The number of chromosomes is here reduces from diploid (2n) to haploid (n). 

In order to achieve genetic diversity, the homologous chromosomes need to separate in the first meiosis, and then the sister chromatids need to separate in the second meiosis, which brings us to four haploid cells. Nondisjunction is an error in this process that can happen in either the separation of homologous chromosomes, or the separation of sister chromatids. The result of nondisjunction in a chromosome imbalance, so a cell that has been affected by nondisjunction is an aneuploid cell. There are different types of aneuploidy, like monosomy (the loss of one chromosome), trisomy (the gaining of one chromosome) and different syndromes can occur as a result of this erroneous process. 

Out of the answers you provided, gaining an extra chromosome would be the answer, but a single chromosome loss can also be the result of nondisjunction.