What are the two major causes of genetic disorders in humans?

• A. Diet and exercise
• B. Changes in the DNA of genes and changes in chromosome structure or number
• C. Infections and injuries
• D. Environmental pollutants only

Answer: (B)

Genetic disorders come from changes in the information stored in our genes. The two major ways this happens are: first, changes in the DNA sequence of individual genes (mutations) that alter a gene’s function; second, abnormalities in chromosome structure or number (such as extra or missing chromosomes, or large structural changes) that affect many genes at once. For example, a single-gene mutation can cause diseases like cystic fibrosis, while having an extra chromosome (Down syndrome) or a missing chromosome can lead to a chromosomal disorder. Diet, exercise, infections, injuries, or environmental pollutants can affect health in many ways, but they are not the primary causes of inherited genetic disorders.