0.000000001
per site per year
0.001
per site per MY
0.000000001
per site per year
0.001
per site per MY
The Nucleotide Substitution Rate calculator estimates how rapidly nucleotide changes accumulate in a lineage over evolutionary time. By combining the evolutionary distance between two sequences with their estimated divergence time, this tool calculates the per-site substitution rate that is fundamental to molecular clock analyses.
Understanding substitution rates is critical for dating evolutionary events, calibrating phylogenetic trees, and comparing the pace of molecular evolution across different genes or organisms. Rates vary widely depending on the organism, gene, and selective pressures involved.
The substitution rate is derived from the evolutionary distance and the time since two lineages diverged:
Rate = Distance / (2 × Divergence Time)
The factor of 2 accounts for the fact that both lineages have been evolving independently since their common ancestor. The divergence time is entered in millions of years and converted to years for the per-year rate. The rate per million years is also provided for convenience.
Inputs
Results
A distance of 0.1 over 50 million years yields a rate of 1 × 10⁻⁹ substitutions per site per year, typical for many nuclear genes in vertebrates.
Inputs
Results
A distance of 0.2 over 10 million years gives 1 × 10⁻⁸ per site per year, roughly 10 times faster than nuclear DNA, which is typical for vertebrate mitochondrial genes.
Because both lineages being compared have been independently accumulating substitutions since they split from their common ancestor. The observed distance is the sum of changes in both lineages, so to get the rate for a single lineage, you divide by twice the divergence time.
For mammalian nuclear DNA, rates are typically around 1-5 × 10⁻⁹ substitutions per site per year. Mitochondrial DNA evolves about 5-10 times faster. RNA viruses can have rates of 10⁻³ to 10⁻⁴ per site per year, many orders of magnitude faster than cellular organisms.
Divergence times are typically estimated from fossil records, biogeographic events, or previously calibrated molecular clocks. Fossil calibration provides minimum divergence times based on the first appearance of diagnostic morphological features. Multiple calibration points are often used to improve accuracy.
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