**Core Concept**
Non-disjunction is a type of error in meiosis or mitosis where a pair of homologous chromosomes or sister chromatids fail to separate properly, resulting in an abnormal number of chromosomes in the daughter cells. This can occur due to errors in the cell cycle, such as mutations in genes involved in DNA replication, repair, or segregation.

**Why the Correct Answer is Right**
Non-disjunction is a well-documented cause of aneuploidy, which is a condition where an individual has an abnormal number of chromosomes. This can lead to various genetic disorders, such as Down syndrome (trisomy 21), Turner syndrome (monosomy X), and Klinefelter syndrome (trisomy X). The mechanism of non-disjunction involves errors in the separation of homologous chromosomes during meiosis I or sister chromatids during mitosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Non-disjunction can indeed result in aneuploidy, so this statement is true.
**Option B:** Non-disjunction is a well-documented cause of genetic disorders, making this statement true as well.
**Option C:** Non-disjunction can occur in both meiosis and mitosis, so this statement is also true.
**Option D:** Non-disjunction is the correct answer for this question, so we will not discuss it here.

**Clinical Pearl / High-Yield Fact**
Non-disjunction is a common cause of aneuploidy, which can lead to various genetic disorders. It is essential to recognize the signs and symptoms of these disorders, such as Down syndrome, Turner syndrome, and Klinefelter syndrome, and to perform diagnostic tests, such as karyotyping, to confirm the diagnosis.

**Correct Answer:** D.