How do chromosomal deletions and duplications affect human development?

Chromosomal deletions and duplications disrupt human development by causing genomic imbalance, which alters the genetic signals necessary for normal growth and function. These structural abnormalities often result in serious developmental consequences because they change the dosage of genes within the affected region.123

• Deletions: The loss of a chromosomal segment is generally lethal or severely damaging. Even small deletions can lead to significant malformations and intellectual disability. A well-known example is cri-du-chat syndrome, caused by a deletion on chromosome 5, which manifests as severe intellectual disability and physical abnormalities.13
• Duplications and Imbalance: When chromosomal material is duplicated or rearranged, it creates an abnormal genetic constitution. While some balanced structural changes may not affect the carrier, they often lead to unbalanced offspring, resulting in syndromes characterized by developmental delays, intellectual disability, heart disease, or other systemic malfunctions.23

These imbalances occur during gamete formation or early embryonic development. Because these conditions fundamentally alter the body's genetic instructions, they are significant causes of developmental disorders and pregnancy loss.2