A less direct method of determining sequence divergence is by

A less direct method of determining sequence divergence is by

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A less direct method of determining sequence divergence is by restriction enzyme mapping . These are enzymes that recognize specific sequences in the DNA and cut the DNA strands. Depending on the location of restriction recognition sites in the DNA, DNA fragments of various lengths will be generated by the restriction enzyme digest resulting in a restriction fragment pattern . One can also determine where various restriction enzymes cut a given piece of DNA and draw up a restriction map of the stretch of DNA. The extent to which two restriction maps (or restriction fragment patterns) are similar serves as an estimator of sequence similarity (or difference). Restriction enzymes will recognize only a fraction of the entire DNA sequence, so one will not know all the differences between two stretches of DNA. The data serve as an estimate and because it usually involved less work can be done on
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Unformatted text preview: many individuals. DNA-DNA hybridization is another indirect way of obtaining estimates of DNA sequence divergence between two taxa. DNA strands are melted apart at high temperature and allowed to "reanneal" in the presence of the DNA of another species. One species' DNA has been labeled with a radioactive nucleotide. This form heteroduplex DNA. The heteroduplex DNA is gradually heated and the amount of single stranded DNA that has "melted" apart is determined by the amount of radioactive label that is counted in each fraction collected from the various temperature steps. Very similar DNA will melt at a high temperature and heteroduplexes between diverged DNAs will melt at a lower temperature. Sequence divergence is proportional to melting temperature ....
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