A SNP (pronounced “snip”) stands for single nucleotide polymorphism. This is a fancy term describing single points in the DNA sequence that differ between animals. The vast majority (~99.9%) of the DNA sequence is identical in all cattle (and people and mice for that matter). There are some locations in the DNA sequence where a single base or a nucleotide (adenine [A], guanine [G], thymine [T], or cytosine [C]) differs from one individual to another. For instance, Bull A may have a DNA sequence of A-G-T-T-C and Bull B may have a sequence of A-G-A-T-C. In this instance, the third base is not the same between these individuals and is called a SNP. There are thousands of SNPs that tell us about an individual’s genetic potential or relationship to another individual. In the past, the ASA used 50K SNP testing (50,000 SNP markers) with GeneSeek and now offers the GGP-HD profile (GeneSeek Genomic Profiler – High Density) with ~80,000 SNP markers. The resulting SNP information is blended with performance records in the ASA genetic evaluation to add molecular breeding values (MBVs) to our EPDs for genomically enhanced EPDs (GE-EPDs). Adding MBVs to our EPDS can improve the accuracy by an equivalent of several progeny records depending on the trait. This is particularly true in young animals that have lower progeny counts and therefore low accuracy EPDs.
In summary, SNPs are points in the DNA where individuals differ accounting for some of the genetic variation we see from animal to animal (and person to person).