Single-nucleotide Polymorphism

First and foremost Single nucleotide polymorphisms, frequently called SNPs or pronounced “ snips”, is a DNA sequence variation occurring when a single nucleotide as A, T, C or G in the genome differs between members of a biological species or paired chromosomes in a human. The less common base must have a frequency of SNPs at least 1 % of the population. For example of SNPs is the substitution of a C for a G in the nucleotide sequence AACGAT, therefore producing the sequence AACCAT.
When SNPs occur inside a gene they create different variants or alleles of those genes. One of the most striking features of this problem is the SNPs’ region occur in noncoding of the genome as well as in genes specificly in both exons and introns. According to research show that SNPs occur once in every 300 nucleotides on average, so in total there are approximately 10 million SNPs in the human genome.

The second thing need to be mentioned is source of polymorphisms. SNPs are created by point mutations normally is any change of single nucleotide at any place in the genome. Some cases can be occur like replacement of one nucleotide with another or delection or addition of a single nucleotide. Single nucleotide polymorphisms are variations in one nucleotide at a very specific locus and mostly have two allles in each locus. SNPs and Genome Wide Association Studies used to determine the functions of genes. Single nucleotide polymorphisms are being very helpful in helping us find that out. These are SNPs which are used to tag specific genotypes. SNPs act as chromosomal tags to specific regions of DNA. Thus, it can be used to identify the location of genes on chromosomes. Non-coding regions that are close to the genome are often the parts that contain the single nucleotide polymorphisms, but it could actually be within a gene also, within a coding region of a gene.

Generally, it is right that adjacent to a gene that we are interested in. It is not in the gene itself. Therefore, there are only two varieties of the alleles.SNPs have some influence central nervous system phenotypes contenting susceptibility to neurological disorders. For example, in Alzheimer’s disease have APOE gene that is an important genetic determinant in disease, encoding apolipoprotein E (ApoE). When two SNPs in this gene presence will create three common variants- APOE ?2, ?3 and ?4, which produce the proteins corresponding is ApoE2, E3, and E4 and each variant have a risk with different level of Alzheimer's disease susceptibility special APOE ?4.

We live in a world, in which have much hidden-danger like cancer. Because some reason, right now SNPs in disease-related genes are increasingly being used as candidates in the search for causative variations. Most SNPs have no effect on health or development. Some of these genentic differences have proven to be very important in the study of human health.
Researchers have found SNPs that may help predict an individual’s response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing particular diseases. SNPs can also be used to track the inheritance of disease genes within families. Future studies will work to identify SNPs associated with complex diseases such as heart disease, diabetes, and cancer.