As often happens in the annals of science, two research teams independently reached the same groundbreaking results, and publication to the scientific world occurred simultaneously. The breakthrough in the present case concerned the mutation rate of DNA and has profound implications for human evolution as well as for DNA Consultants’ new offerings in autosomal DNA ancestry analysis, specifically our Rare Genes from History Panel.
The following two studies are already much cited by geneticists, though they have garnered little attention in the press. They appeared in online versions on the same day, August 23.
James X Sun et al., “A Direct Characterization of Human Mutation Based on Microsatellites,” Nature Genetics 44/10 (October 2012): 1161-65.
A. Kong et al., “Rate of de novo Mutations and the importance of Father’s Age to Disease Risk,” Nature 488 (2012):471-75.
A table summarizing their findings and older data is provided below for DNA testing customers’ convenience.
DNA Mutation Rates
|Study or Source||Type of DNA||Sample or Method||Rate per Generation||Time Depth in Years|
|Sun 2012||autosomal microsatellites||2,477 mutations in Icelanders||.001- .0001||25,000 to 250,000|
|Kong 2012||single nucleotide polymorphisms||4,933 mutations in Icelandic trios||63.2 or .000000012||Very great|
|Butler 2009||Core CoDIS STRs (microsatellites)||compiled from studies||.0028-.0001||9,000 to 25,000|
|Zhivotovsky 2004||Y chromosome STRs||Y haplogroup comparisons||.00069||36,000|
|Heyer 1997||Y chromosome tetranucleotides||42 males in forensic database||.002||12,500|
|FamilyTreeDNA 2004||Y chromosome STRs||Estimated from customer base||.004||6,250|
|Brinkmann 1998||STRs (CoDIS markers)||10,844 Father-son comparisons||0-.007||3,500 to Very Great|
|Parsons 1997||mitochondrial DNA||134 mtDNA lineages||.000029||862,000|
|DNA Consultants||Rare Genes from History||average estimate across loci||.001325||19,000|
From this it can be seen that mutation rates vary from a low with SNPs to the high rate of Y chromsome STRs (as much as 0.4 % per generation). DNA keeps surprising us by proving to be more stable than we would tend to expect, dutifully transcribing its original values from generation to generation without many mistakes or changes. Only Y chromosome seems to be highly changeable, depending on the father’s age (Kong 2012). Autosomal STRs mutate at a rate between SNPs and the Y chromosome, between every 19,000 or 25,000 and 250,000 years.
For our new autosomal ancestry markers, that is confirmation that the alleles we are examining on a statistical basis are pretty much unchanged for the past 20,000 years. That’s about twice the length of what we call world history, hence a meaningful enough time frame for valid inferences about population patterns and ancestry of individuals.
A change in a DNA sequence, either spontaneous within a generation or inherited, sometimes from a very distant ancestor. Mutations usually do not affect our health or cause any differences in our appearance. In other words, they are not genes proper and do not “code” for new proteins. Even though they are non-coding genes, though, they are useful in tracing lineages.From A Glossary of Common DNA Terms