But... the DNA does become tangled... more accurately described as knotting. The healthy strands of DNA within the cell are tightly coiled. Usually, when a strand is replicated, only a small section is unwound and the surgery is completed. However, for reasons not entirely clear, when DNA strands are "snipped" by enzymes to rearrange its genetic sequencing in a process known as recombination the usually neat and tidy DNA ladder can become hopelessly tangled or knotted.
Fortunately, other enzymes can cleanup the mess, but in some instances, deterioated DNA is the result.
Recent studies have shown that site-specific recombination can twist the DNA only into particular, definaeable knots and links. Its been found that only a small proportion of the very complicated knots could occur in DNA. The experiments indicate the possibility that the enzymatic action could help researchers use site-specific recombination to repair the faulty DNA that causes genetic diseases. (Thanks in part to: Science News)