BCMB 402 Site-specific recombination and transposition of DNA 1.ppt

Site-specific recombination and transposition of DNA 1 Chapter 11 pp 319-324; 326; 329-332;334-339 Site specific recombination and transposition are two classes of genetic recombination Types of conservative site-specific recombination (CSSR) Symmetric recombination sites flank the DNA sequences where recombination occurs Site specific recombinases use a protein-DNA intermediate that is covalently linked Serine recombinases promote Double strand breaks and swap strands to promote recombination Tyrosine recombinases promote single strand breaks and rejoin a pair of single DNA strands at a time to promote recombination l integrase promotes integration and excision of the l phage into the bacterial genome lIntegrase (a tyrosine recombinase) catalyzes recombination between attB and attP sites lintegrase and accessory proteins DNA inversion induced by the Hin recombinase mediates activation of alternative forms of Flagellin Transposition consist on the movement of a genetic element to a new site on the chromosome May insert in genes disrupting gene function (natural mutagenic agents) May insert within regulatory sequences changing the patterns of expression of genes. Several human diseases are caused by Transposable elements (hemophilia A and B, severe combined immunodeficiency, porphyria, predisposition to cancer or Duchenne muscular dystrophy) Occurrence and distribution of TEs strongly depends on organisms There are three major classes of TEs LTR retrotransposons Non-LTR retrotransposons