Final answer:
Turner syndrome (XO) is caused by having one copy of the X chromosome, known as monosomy. The aneuploid gamete that caused this condition could have been generated through nondisjunction during the production of the mother's egg.
Step-by-step explanation:
Turner syndrome (XO) is caused by having just one copy of the X chromosome, which is known as monosomy. One way an aneuploid gamete that caused this condition could be generated is through nondisjunction during the production of the mother's egg. Nondisjunction occurs when homologous chromosomes fail to separate during meiosis I or sister chromatids fail to separate during meiosis II, resulting in the production of gametes with an incorrect number of chromosomes.