A friend who works in a research lab performed a GWAS and discovered a tight association between a SNP allele and the disease she is studying. She concluded that the SNP allele must be the mutation that causes the disease. Explain why she is likely to be wrong.

Verified step by step guidance

1. Understand the concept of SNP (Single Nucleotide Polymorphism): SNPs are variations at a single position in DNA among individuals. They are the most common type of genetic variation in humans.
2. Recognize the nature of GWAS (Genome-Wide Association Studies): GWAS are studies that involve scanning markers across the genomes of many people to find genetic variations associated with a particular disease. However, these studies only show associations and do not prove causation.
3. Consider Linkage Disequilibrium: SNPs found to be associated with a disease in GWAS may be in linkage disequilibrium with the actual causal mutation. This means the SNP is near the true causal genetic variant and inherited together with it, but is not itself the cause of the disease.
4. Evaluate the need for further research: To establish causality, further studies such as functional genomics or experimental validation are needed. These studies can help determine if the SNP directly affects the biological pathway of the disease.
5. Explore alternative explanations: It's also possible that multiple SNPs or a combination of genetic and environmental factors contribute to the disease, rather than a single SNP being the sole cause.

Key Concepts

Genome-Wide Association Studies (GWAS)

GWAS are research methods used to identify genetic variants associated with specific diseases by scanning the genomes of many individuals. They focus on single nucleotide polymorphisms (SNPs) to find correlations between genetic variations and phenotypic traits. However, GWAS can only show associations, not causation, meaning that while a SNP may be linked to a disease, it does not necessarily mean it causes the disease.

Causation vs. Correlation

Causation refers to a direct cause-and-effect relationship, while correlation indicates a statistical association between two variables without implying that one causes the other. In the context of GWAS, a SNP may correlate with a disease, but other factors, such as environmental influences or nearby genes, could be responsible for the observed association, leading to potential misinterpretation of the SNP's role.

Genetic Heterogeneity

Genetic heterogeneity occurs when a single phenotype or disease can be caused by different genetic mutations or variations. In diseases, multiple SNPs or other genetic factors may contribute to the same condition, complicating the interpretation of GWAS results. This means that the identified SNP allele may be associated with the disease but not be the sole cause, as other genetic or environmental factors could also play significant roles.