• Introduction to Molecular Genealogy
• Family Tree
• DNA Testing
• Your DNA
• Mitochondrial DNA
• Y Chromosome DNA
• Autosomal DNA
• X Chromosome DNA
• Haplogroups
• Mutation and Haplotypes
• Putting it all together
• How to use a DNA kit
• Understanding your results

Mutation and Haplotypes: The Path to a Common Ancestor

Although the four types of DNA are inherited in very different ways, they are all prone to mutation. The molecular machines that copy DNA make occasional errors, called mutations (some mutations cause disease, but most are harmless). As DNA is copied and passed down through generations, it gradually accumulates mutations, or differences. People who are more closely related have fewer differences among their DNA profiles than people who are more distantly related.

DNA can be tested at specific locations known as markers. Each marker has specific variations called alleles. In most cases, knowing an allele value for a single DNA marker doesn’t tell you very much. But because DNA tends to be inherited in large chunks, looking at allele values for several markers across a stretch of DNA can be very informative.

A haplotype is a set of allele values across a stretch of DNA that is inherited together (as a chunk). People with the same haplotypes for a certain region of DNA are more closely related than those with different haplotypes. Since scientists have been able to determine the average rates of mutation for DNA markers, the number of differences between your haplotype and that of another person can tell you approximately how far back in time you have to go to find a common ancestor.