What may a cell splitting without proper duplication genes result in?
Answer:
Animal cells have very effective "checkpoints" and "surveyance" to avoid this happening, so most aneuploid cells do not survive. However, when they do, various things can result depending on the cell(s) involved:

Gametes (Egg or sperm): Can result in trisomy 21 (Down's syndrome baby) and other very rare conditions.

Stem cells (Fertilized egg): Depends on what stage it happens, but usually leads to spontaneous abortion (miscarriage).

Somatic cells (differentiated cells like skin, muscle, fat): Can result in tumor growth and ultimately cancer.

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