In the human body, chromosomes are the structures that hold genes. They give instructions and tell the bodies how to develop and function. In fact, they govern physical characteristics such as eye color, hair color, skin color and also the medical characteristics of the body such as blood type and susceptibility to disease.
A chromosome abnormality is caused when there is any disorder in DNA which may have been caused due to mutation or a missing or extra portion of chromosomal DNA.
Chromosomal abnormalities may be caused due to Mitosis, Meiosis, Environment and even the maternal age. If they become pregnant, Older women are at a higher risk of giving birth to abnormal babies than young mothers.