SNPs

• • A SNP is single nucleotide base change in a DNA sequence which are scattered throughout the genome across multiple chromosomes.
• • They usually arise during DNA replication, where a single nucleotide is incorrectly inserted creating an error in the DNA sequence at a particular location on a chromosome. The change in DNA needs to occur in at least 1% of the population before it can be termed a SNP (rather than simply a point mutation).
• • Most SNP’s lead to no observable differences between people at all because most occur in the non-coding regions of DNA. However, some SNPs occur in the coding regions of DNA and may be associated with phenotypic changes.
• • SNP’s are important genetic markers (identified sequence of DNA at a known site on a chromosome) because they are the most common type of genetic variation between individuals.
• • genetic screening for the presence of disease genes, e.g. sickle cell anaemia, cystic fibrosis
• • tracking family inheritance of diseases and help predict an individual’s risk of developing particular diseases
• • studying ancestry (so evolution of humans and other species) - if people share many of the same SNPs, then that shows they are closely related and have a common ancestry (share a common ancestor)
• • pharmacogenetics to help predict an individual’s response to certain medications and therefore provide personalised medications