Table 3.
Sensitivity and Specificity of Single Perfect Nucleotide K-mer Matches as a Search Criterion
| 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | |
|---|---|---|---|---|---|---|---|---|
| A. 81% | 0.974 | 0.915 | 0.833 | 0.726 | 0.607 | 0.486 | 0.373 | 0.314 |
| 83% | 0.988 | 0.953 | 0.897 | 0.815 | 0.711 | 0.595 | 0.478 | 0.415 |
| 85% | 0.996 | 0.978 | 0.945 | 0.888 | 0.808 | 0.707 | 0.594 | 0.532 |
| 87% | 0.999 | 0.992 | 0.975 | 0.942 | 0.888 | 0.811 | 0.714 | 0.659 |
| 89% | 1.000 | 0.998 | 0.991 | 0.976 | 0.946 | 0.897 | 0.824 | 0.782 |
| 91% | 1.000 | 1.000 | 0.998 | 0.993 | 0.981 | 0.956 | 0.912 | 0.886 |
| 93% | 1.000 | 1.000 | 1.000 | 0.999 | 0.995 | 0.987 | 0.968 | 0.957 |
| 95% | 1.000 | 1.000 | 1.000 | 1.000 | 0.999 | 0.998 | 0.994 | 0.991 |
| 97% | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 0.999 |
| B. K | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 |
| F | 1.3e+07 | 2.9e+06 | 635783 | 143051 | 32512 | 7451 | 1719 | 399 |
(A) Columns are for K sizes of 7–14. Rows represent various percentage identities between the homologous sequences. The table entries show the fraction of homologies detected as calculated from equation 3 assuming a homologous region of 100 bases. The larger the value of K, the fewer homologies are detected.
(B) K represents the size of the perfect match. F shows how many perfect matches of this size expected to occur by chance according to equation 4 in a genome of 3 billion bases using a query of 500 bases.