The main difference between SNP and STR is that SNPs are variations in a single nucleotide at a specific position in the genome, whereas STRs are variations in the number of repeats of a short DNA sequence.
A genetic marker is a sequence of DNA or a gene with a known physical location on a chromosome. It can help to identify individuals or species. A genetic marker can be a long DNA sequence like minisatellites or a short DNA sequence such as a sequence surrounding a single base pair change. Moreover, some examples of common genetic markers are RAPD, SSLP, SFP, RAD, AFLP, SNP, and STR.
Key Areas Covered
1. What is SNP
– Definition, Features
2. What is STR
– Definition, Features
3. Difference Between SNP and STR
– Comparison of Key Differences
Key Terms
SNP, Single Nucleotide Polymorphism, STR, Shorte Tandem Repeat
What is SNP
SNP or single nucleotide polymorphism is a mutation in one of the nucleotide bases of the DNA. This SNP is used as a biological marker in the study of biological phenomena. SNPs are present in different parts of the genome, both in the coding and non-coding regions. They also have functional and non-functional effects on gene expression and protein function.
SNP has been very stable over many generations. Once a mutation occurs, it is carried by the next generations (the descendants) of the individual in whom the SNP was formed (the SNP progenitor). Hence, SNP DNA is useful to distinguish one genetic lineage from the other.
SNPs are biallelic (they have two possible alleles). SNPs are more common in the genome. They are useful in genetic association studies. They are also useful as genetic markers in population studies, for example, in the identification of different ethnic groups.
SNP may not capture all of the genetic variations with a given gene or region of the genome. This is because they only represent a single nucleotide change. Hence, they are not useful in certain applications, such as deletions in the genomes or identifying structural variants or large insertions.
What is STR
STR stands for a short tandem repeat. These short tandem repeats are repeating sequences of DNA that are typically between 2-6 base pairs in length. These repeats are present in various regions of the genome, including coding and non-coding regions. In fact, STRs are small in size and tend to mutate rapidly.
STR is a molecular biology method that helps to compare allele repeats at specific loci (positions) in DNA between two or more samples. Furthermore, STRs are genotyped using methods including capillary electrophoresis and PCR.
STRs have important usage in many different functions, such as forensic analysis, population genetics, and in disease research. Among them, the most significant use of STRs is in forensic analysis. The number of repeats at multiple STR loci is compared to determine a DNA profile. Moreover, the fact that the probability of two individuals having the same DNA profile is extremely low makes the STR analysis a powerful tool in criminal investigations and paternity testing.
In population genetics, STRs are useful in the study of the genetic diversity of populations. Determination of the relatedness of populations to each other is done by the analysis of the frequency of different alleles at multiple STR loci. Additionally, this is useful for tracing human migration patterns and understanding the basis of complex diseases.
STRs are also useful in disease research. Analyzing the number of repeats in affected individuals and their family members helps to identify the risk of the development of a certain disease.
Difference Between SNP and STR
Definition
SNPs are variations in a single nucleotide at a specific position in the genome, whereas STRs are variations in the number of repeats of a short DNA sequence.
Frequency
SNPs are the most common type of genetic variation. They are found throughout the genome with a frequency of about one SNP per every 300 bases of DNA, whereas STRs are less common and occur in fewer places in the genome.
Diversity
Moreover, SNPs are less diverse than STR, as they usually have only two alleles. In contrast, STRs have multiple alleles, with each allele representing a different number of repeats of the tandem sequence.
Applications
SNRs are used in genome-wide association studies to identify genetic factors associated with complex diseases, while STRs are used in forensic studies, paternity testing, and population genetics studies.
Conclusion
In brief, a genetic marker is a sequence of DNA or a gene with a known physical location on a chromosome. SNP and STR are two common examples of genetic markers. The main difference between SNP and STR is that SNPs are variations in a single nucleotide at a specific position in the genome, while STRs are variations in the number of repeats of a short DNA sequence.
Reference:
1. “A Brief Review of Short Tandem Repeat Mutation.” National Library of Medicine.
2. “What are single nucleotide polymorphisms (SNPs)?” MedlinePlus. National Library of Medicine.
Image Courtesy:
1. “SNP-Dash-1updated” (CC BY-SA 3.0) via Commons Wikimedia
2. “Str profile” By Sekiyu at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
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