2017+lecture+21+TEs+and+variations+in+CNs+posted.

transposable elements = jumping genes discovered by Barbara McClintock in maize transposable elements = jumping genes first evidence by Marcus Roades in 1930s and described in detail by Barbara McClintock in maize from 1940 onwards but they exist in many organism including mammals, insects, plants…… the human genome Classification two different major classes RETROTRANSPOSONS - RETROPOSONS transpose via reverse transcription of an RNA intermediate TRANSPOSONS transpose DNA directly without an RNA intermediate • many different types • some with cool names: mariner, gypsy, looper, springer, hopper, stalker, invader, diver, frogger • can be 50 bp to 10 kb in length • different copy numbers: one to 100 thousands • “selfish” • carrying only information that allows their self-perpetuation • however, there are examples where they have functions in the host • maintain telomere length in non-LTR LINEs: long interspersed elements L1: app. 20000 copies, 6.4 kb SINEs: short interspersed elements Alu: app. copies, 0.28 kb LTR: long terminal repeats appr. 45% of the total genome ......................................CONTINUED.........................................