Single Nucleotide Polymorphisms
Mutations provide the raw material for genetic variation, and come about through mistakes when DNA is copied or environmental factors, such as ultraviolet radiation from the sun. A mutation is a permanent change in the sequence of DNA. Mutations range in size from a change in a single DNA base (point mutation) to a change in a large segment of a chromosome. When a single nucleotide at the same location differs between individuals, the variation is called a “snip” (short for single nucleotide polymorphism or SNP).
Image Note: DNA has two strands (shown here as red and green), and four nucleotides (A T G C) that pair: A-T, and G-C. Genetic information is stored in the exact list, or sequence of nucleotides, like a computer stores data as a long precise list of 1's and 0's.
Only one strand is sequenced, in this case, the green strand.
5. Use this slide, to further explain the DNA molecule and SNPs. Tell students that biologists now can identify the sequence of nucleotides in a section of DNA. Usually, there are many differences in the DNA from one individual organism to another member of the same species. Most differences do not cause any observable changes or diseases. However, sometimes a mutation (change in the DNA sequence) causes some individuals to be different. By comparing the DNA sequences of two different groups, biologists sometimes can find the genetic change responsible for variation among individuals.
Keywords: adenine | allele | biology | cell | chromosome | cytosine | DNA | double helix | gene | genetic | genetic code | genetics | genetics | genome | genotype | guanine | life science | nucleotide | nucleotide base | nucleus | SNP | thymine | lesson
- Moreno, N. (2017) Complex Traits: Using Dogs as a Model for Modern Genetics. Baylor College of Medicine: Houston. ISBN: 978-1-994035-08-2.
- SNP graphic by David Hall, courtesy of NIH.
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