What is the Difference Between SNP and CNV

The main difference between SNP and CNV is that SNP, or single nucleotide polymorphism, is the substitution of a single nucleotide in the germline cells, whereas CNV, or copy number variation, is the duplication or deletion of a considerable number of nucleotides in the genome.

SNP and CNV are two types of nucleotide changes that can occur in the genome of organisms. They cause variations in the genome.

Key Areas Covered

1. What is SNP
      – Definition, Structure, Function
2. What is CNV
     – Definition, Structure, Function
3. Similarities Between SNP and CNV
     – Outline of Common Features
4. Difference Between SNP and CNV
     – Comparison of Key Differences

Key Terms

CNV, Copy Number Variation, SNP, Single Nucleotide Polymorphism

What is an SNP

SNP or single nucleotide polymorphism is a nucleotide substitution of the germline cells. A single nucleotide variation is classified as a single nucleotide polymorphism when a substantial proportion of the population possesses the variation. Generally, 1% of the population needs to have the variation. For instance, a specific base position of the genome contains a G nucleotide. But the minority of individuals may have the nucleotide A. Therefore, the two possible variations of the nucleotide position are G and A.

Figure 1: SNP

SNP occurs in the germline cells. The main feature of SNP is that it makes individuals susceptible to diseases. One example of such a disease is age-related macular degeneration. Generally, a common SNP in the CFH gene increases the risk of the disease. Another example of SNP-related disease is non-alcoholic fatty liver disease. It occurs due to the presence of an SNP in the PNPLA3 gene of the genome.

What are CNV

CNV, or copy number variation, is a molecular phenomenon in which the sequences of the genome are repeated. The number of repeats of CNV in the genome varies among individuals. CVN in organisms can lead to a range of effects, including variations in physiological traits, changes in metabolic states, alterations in morphology, increased susceptibility to infectious diseases, and impacts on host-microbiome interactions. Moreover, CNV contributes to both common and rare genetic disorders. The main importance of CNV in the genome is that it contributes to the diversity of the human population. In addition, CNV contributes to micro- and mini-evolutionary changes in the human population.

Figure 2: CNV

Moreover, CNV is important as a biomarker for certain pathological processes such as cancer. It is also important as a biomarker for exposure to radiation. However, over 100 genes are hemizygously deleted from the human genome.

CNV is the main type of structural variation in the genome. It is a duplication or deletion of a considerable number of base pairs in the genome. There are two main groups of CNV: short repeats and long repeats. Short repeats include dinucleotide and trinucleotide repeats, while long repeats include the repeats in the entire genes.

Similarities Between SNP and CNV

• SNP and CNV are two types of nucleotide changes that can occur in the genome of organisms.
• Both bring variations in the genotype, and they can cause genetic diseases.

Difference Between SNP and CNV

Definition

SNP refers to a genomic variant at a single base position in the DNA while CNV refers to a phenomenon in which sections of the genome are repeated, and the number of repeats in the genome varies between individuals.  

Type of Substitution

SNP is a nucleotide substitution, while CNV is a duplication or deletion of nucleotides.

Number of Base Pairs

Moreover, SNP is a single nucleotide substitution, while CNV affects a considerable number of base pairs in the genome.

Effect on the Genome

SNP passes into the next generation as it occurs in the germline cells, while CNV is the major cause of structural variation in the genome.

Conclusion

In brief, SNP and CNV are two types of nucleotide changes that can occur in the genome. Both bring variations to the organism and cause genetic diseases in the organism. SNP is a single nucleotide substitution that occurs in the germline cells. Therefore, it passes to the next generation. In comparison, CNV is a duplication or deletion of nucleotides in the genome. It is the main cause of structural variation in the genome. Therefore, the main difference between SNP and CNV is the effect on the genome.  

References:                     

1. “SNP.” Nature news. Nature Publishing Group. 
2. Pös O, Radvanszky J, Buglyó G, Pös Z, Rusnakova D, Nagy B, Szemes T. “DNA copy number variation: Main characteristics, evolutionary significance, and pathological aspects.” Biomed J. 2021 Oct;44(5):548-559. doi: 10.1016/j.bj.2021.02.003. Epub 2021 Feb 13. PMID: 34649833; PMCID: PMC8640565.

Image Courtesy:

1. “Dna-SNP” By David Eccles – Own work (CC-BY 4.0) via Commons Wikimedia
2. “Gene-duplication” By National Human Genome Research Institute – Own Work (Public Domain) via Commons Wikimedia