Genetic Variation: Why Are We Different?
It is easy to understand, highly visual, and connects naturally :
to DNA → genes → genomes → mutations → genomics. NHGRI defines genomic variation as differences in DNA sequence among individuals or populations, with some variants affecting biological function and others having no known effect.
Where Does Genetic Variation Come From?
Genetic variation can arise through different biological processes, including DNA changes, recombination, and inheritance.
Some DNA changes occur naturally during DNA replication, while others can result from environmental factors that damage DNA. Mutations are changes in DNA sequence, but not every genetic change has a harmful effect.
A Simple Example
Imagine two DNA sequences:
Person A:
A T G C C A T G
Person B:
A T G T C A T G
One DNA base is different.
This is an example of a single-nucleotide variation. A common type is called a single-nucleotide polymorphism (SNP).
Common Types of Genetic Variation
Genetic variation can take several forms:
- SNPs — variation at a single DNA base
- Insertions — additional DNA sequence
- Deletions — missing DNA sequence
- Copy-number variations — differences in the number of copies of a DNA segment
- Larger genomic changes — structural differences involving larger regions of DNA
Does Genetic Variation Always Cause Disease?
No.
Some genetic variants can influence biological characteristics or disease risk, while others have little or no known effect. Understanding the biological and clinical significance of a particular variant can be complex.
This is why researchers study genetic variation across individuals and populations.
Why Is Genetic Variation Important?
Genetic variation helps researchers understand:
- Human biological diversity
- Inheritance
- Evolution
- Genetic diseases
- Disease-associated variants
- Drug response
- Population genetics
- Genomics
Modern genomic databases and sequencing technologies allow scientists to identify and study genetic variants on a large scale.
Explore Genetic Variation
Want to learn more?
- NHGRI Talking Glossary of Genetic Terms — Explore terms such as allele, mutation, genomic variation, genotype, and SNP.
- NCBI — Genetics 101 — Learn the fundamentals of DNA, genes, genomes, and genetic variation.
- NCBI Variation Resources — Explore databases and tools for studying genetic variation.
- NHGRI Fact Sheets — Explore accessible resources about genetics and genomics.