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Nondisjunction

APBIO-06Y7SE

Nondisjunction is the failure of homologous chromosomes to separate properly during meiosis. Below is a karyotype of a person that is the product of a nondisjunction event.

Karyotype of X Monosomy (Turner Syndrome). Digital image. Wikipedia. N.p., 17 Oct. 2006. Web. 9 Mar. 2016.

Which of the following statements below could predict the events that occurred to produce the individual shown in the karyotype above?

A

Because this individual was female, one X chromosome was inactivated. This inactivation prevents the appearance of two X chromosomes on the karyotype.

B

While the cells that gave rise to this individual were forming, one of the gametes became cancerous. Errors in cell division caused by cancer produced the karyotyped individual with an abnormal chromosome number.

C

During meiosis, two X chromosomes combined to make one larger-than-average X chromosome. Because the amount of DNA in the cell is unchanged, this had no effect on the development of the karyotyped individual.

D

A mistake was made during meiosis, resulting in either the sperm or the egg missing its sex chromosome. Fertilization of this unusual gamete produced an individual with only 45 chromosomes.