विस्तृत व्याख्या:

Non-disjunction (अवियोजन):

• Non-disjunction is the failure of homologous chromosomes to separate during Meiosis I (Anaphase I) or the failure of sister chromatids to separate during Meiosis II (Anaphase II).
• Meiosis I Non-disjunction: Leads to 100% abnormal gametes ($n+1, n+1, n-1, n-1$).
• Meiosis II Non-disjunction: Leads to 50% abnormal gametes ($n+1, n-1$) and 50% normal gametes ($n, n$).
• Fertilization of these abnormal gametes leads to aneuploidy (e.g., trisomy $2n+1$ such as Down syndrome or monosomy $2n-1$ such as Turner syndrome).
• Translocation and Inversion are structural chromosomal aberrations, while Insertions are gene-level mutations.

Correct Answer: Option 3 (Non-disjunction).