The primary difference between microsatellites and SNPs lies in their nature, abundance, and informativeness as genetic markers: SNPs are more abundant but less informative due to being diallelic, while microsatellites are less abundant but more informative due to having multiple alleles.
Here's a more detailed breakdown:
Microsatellites (Short Tandem Repeats - STRs)
- Nature: Microsatellites, also known as Short Tandem Repeats (STRs), are repetitive DNA sequences typically 2-6 base pairs long that are repeated multiple times in tandem. For example, (CA)n, where 'n' is the number of repeats.
- Alleles: These repeats are highly polymorphic, meaning the number of repeats can vary greatly between individuals, leading to many different alleles at a single locus.
- Abundance: Less abundant compared to SNPs.
- Informativeness: Highly informative due to the large number of alleles per locus (multiallelic).
- Mutation Rate: Higher mutation rate than SNPs. This high mutation rate is what gives rise to the high variability in repeat number.
- Applications: Widely used in DNA fingerprinting, population genetics, and linkage analysis.
Single Nucleotide Polymorphisms (SNPs)
- Nature: SNPs are single base-pair variations in the DNA sequence.
- Alleles: Typically bi-allelic, meaning only two possible alleles exist at a single SNP locus.
- Abundance: Extremely abundant throughout the genome, making them a valuable resource for genetic studies.
- Informativeness: Less informative per locus compared to microsatellites due to being bi-allelic. A larger number of SNPs are required to achieve the same level of informativeness as microsatellites.
- Mutation Rate: Lower mutation rate than microsatellites.
- Applications: Widely used in genome-wide association studies (GWAS), pharmacogenomics, and personalized medicine.
Summary Table: Microsatellites vs. SNPs
| Feature | Microsatellites (STRs) | SNPs |
|---|---|---|
| Nature | Repetitive DNA | Single base-pair variation |
| Alleles | Multiallelic | Bi-allelic |
| Abundance | Less abundant | Highly abundant |
| Informativeness | High | Lower |
| Mutation Rate | Higher | Lower |
In conclusion, while both microsatellites and SNPs are valuable genetic markers, they differ significantly in their characteristics. SNPs are more abundant and easier to genotype on a large scale, making them suitable for genome-wide studies. Microsatellites, with their higher informativeness per locus, are often preferred when a smaller number of highly informative markers are needed.
