single nucleotide polymorphism<br /><br /p>한개의 염기서열의 차이를 이용하는 것을 말한다. <br /><br />1번 개체 AC<strong>C</strong>ATG<br />2번 개체 AC<strong>T</strong>ATG <br /><br />두 개체간의 염기서열의 차이를 이용하게 된다.<br /><br />예를 들어 특정 질병에 잘 걸리는 집단과 잘 걸리지 않은 집단간의 유전자 차이를 비교할 떄 비교, 질병의 원인을 규명혹은 마커 발견 할 때 유용하게 쓰이게 된다. <br /><br /><font size="3"><strong>[Definition]</strong><br />SNPs are single base pair positions in genomic DNA at which different <br />sequence alternatives (alleles) exist in normal individuals in some <br />population(s), wherein the least frequent allele has an abundance <br />of 1% or greater. </font></p><p><font size="3"><strong>[Narrow scope]</strong> <br />Single base insertion/deletion variants (indels) would not <br />formally be considered to be SNPs. </font></p><p><font size="3"><strong>[Pronunciation]</strong><br />SNP (pronounced 'S' 'N' 'P' or 'SNiP') </font></p><p><font size="3"><strong>[Characteristics of human SNPs]<br /></strong>Understand human DNA polymorphism, about 90% of which is <br />single nucleotide polymorphism (SNP) </font></p><p><font size="3">SNPs could be bi-, tri-, or tetra-allelic polymorphisms. <br />However, in humans, tri-allelic and tetra-allelic SNPs are rare almost <br />to the point of non-existence, and so SNPs are sometimes simply <br />referred to as bi-allelic markers (or di-allelic) </font></p><p><font size="3">The typical frequency with which one observes single base differences in genomic <br />DNA from two equivalent chromosomes is of the order of 1/1000 bp = 0.1% </font></p><p><font size="3">cf) non-coding HLA regions show nucleotide diversity levels of 5–10% <br /><br /></font><font size="3"><strong>[Application]<br /></strong><br />Population genetics and linkage disequilibrium :<br />The study of the genetic composition and inter-relationships between <br />populations. The major research tool it uses is DNA polymorphism. </font></p><p><font size="3">Complex phenotypes and genome variation :<br />Risks of major common diseases such as cancer, cardiovascular disease, <br />mental illness, auto-immune states, and diabetes, are expected to be heavily<br />influenced by the patterns of SNPs one possesses in certain key susceptibility <br />genes yet to be identified. </font></p><p><font size="3">SNP based association studies :<br />If a factor contributes an increased risk for disease occurrence, then that factor <br />should be found at higher frequency in individuals with that disease compared to <br />non-diseased controls </font></p><p><font size="3"><strong>[Reference]</strong><br />Brookes AJ, The essence of SNPs, Gene. 1999 Jul 8;234(2):177-86.<br /></font><br /></p>
