Single nucleotide polymorphism
Single nucleotide polymorphism (SNP) refers to the difference of single nucleotide at the same position in the genomic DNA sequence. In general, a single nucleotide variation with a frequency greater than 1% is called an SNP. The SNPs involve only a single base variation, which can be caused by a single base transition or transversion. There is approximately one SNP per 1000 bases in the human genome, and the total number of SNPs in the human genome is around 3 x 106.
SNP has become the third generation of genetic markers. The characteristics of SNPs make them more suitable for studies on genetic pleiotropy in complex traits and diseases, and population-based gene recognition than other polymorphic markers. SNPs have significant importance in biomedical research. SNPs have been used in genome-wide association studies as high-resolution markers in gene mapping related to diseases or normal traits. SNPs without an observable impact on the phenotype (called silent mutations) may also be useful due to their quantity and stable inheritance over generations.
Figure 1. The upper DNA molecule differs from the lower DNA molecule at a single base-pair location (a C/A polymorphism).
The DNA microarray refers to a gene chip with a large number of probe DNA sequences in a specific arrangement immobilized on a solid substrate. The principle is the nucleic acid hybridization theory, and the detected sample DNA is hybridized with the DNA microarray and extended. Subsequently, the fragments of the non-complementary binding reaction on the chip are washed away, and the gene chip is subjected to laser confocal scanning. Fluorescence signal intensities are then measured and interpreted as the abundance of different genes through certain data processing.
Figure 2. The principle of microarray.
SNP microarray uses known nucleotide sequences as probes to hybridize with the tested DNA sequences, allowing qualitative and quantitative SNP analysis through signal detection. Compared with the traditional single cell diagnostic method, SNP microarray is a high throughput method, which is capable of performing thousands of reactions on the surface of the oligonucleotide chip at one time.
The workflow of SNP microarray
The general workflow of SNP microarray is shown in figure 3. Briefly speaking, there are several processes: SNP chip fabrication, sample genomic DNA preparation, hybridization, and fluorescence scanning.
Figure 3. The workflow of SNP microarray.
At CD Genomics, we are dedicated to providing reliable SNP genotyping services, including genotyping by sequencing, SNP microarray, MassARRAY SNP genotyping, SNaPshot Multiplex System for SNP genotyping, and TaqMan SNP genotyping.