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How can harmful genetic variations contribute to disease?
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human genome
The human genome is made up of approximately three billion base pairs of deoxyribonucleic acid (DNA). The bases of DNA are adenine (A), thymine (T), guanine (G), and cytosine (C).
Harmful genetic variations contribute to disease by altering the structure or function of proteins, which are essential for carrying out cellular functions. When DNA sequences are mutated, the resulting defective synthesis can lead to malfunctioning proteins, particularly if the affected protein is a critical enzyme in normal metabolism.1
These variations can manifest in several ways:
- Point Mutations: Small changes, such as base substitutions, can lead to missense mutations (altering protein function) or nonsense mutations (causing premature termination of protein synthesis).2
- Frameshift Mutations: The addition or deletion of DNA bases shifts the reading frame, often resulting in a functionless protein.2
- Single Nucleotide Polymorphisms (SNPs): While most SNPs are harmless, some contribute to the development of diseases like cancer or influence how individuals respond to drugs.3
- Polygenic Inheritance: Many birth defects result from the combined effect of multiple genes and environmental factors, where susceptibility is continuously variable until a developmental threshold is exceeded.4
Mutations in germ cells are inherited, while somatic mutations can cause conditions like cancer within an individual.21