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The Nature of Transposons Chapter 11 pp 297-309

The Nature of Transposons Chapter 11 pp 297-309. Outline. Nature of Transposons Transposons Prokaryotic Eukaryotic: Dr. McClintock’s research Retrotransposons vs Retroviruses. Transposons. Are mobile DNA sometimes referred to as “jumping genes”.

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The Nature of Transposons Chapter 11 pp 297-309

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  1. The Nature of TransposonsChapter 11 pp 297-309

  2. Outline • Nature of Transposons • Transposons • Prokaryotic • Eukaryotic: Dr. McClintock’s research • Retrotransposons vs Retroviruses

  3. Transposons • Are mobile DNA sometimes referred to as “jumping genes”.

  4. Common features associated with transposons 1. Direct repeats Common Features Are: 2. Terminal Inverted repeats

  5. Transposable Elements in Bacteria

  6. 1. Simple Bacterial Transposon INSERTION SEQUENCE

  7. 2. COMPOSITE TRANSPOSON IS + any DNA segment

  8. Dr. Barbara McClintock 1902-1992 Nobel Prize, 1983 Physiology or Medicine

  9. “I don’t understand a word that she said, but if she says it is so, it must be so!”Alfred Sturtevant

  10. “Ds Transposed out”

  11. The Ds element often results in chromosomal breakage

  12. Drosophilia melanogaster& DNA transposition“The P Element”

  13. The P element Codes for • Transposase • Repressor of transposition

  14. Female P- and male P+ Female P+ and male P- Offspring sterile Offspring normal Non-hybrid dysgenesis Hybrid dysgenesis Why the difference?

  15. Remember the P element Codes for • A Transposase • AND • A Repressor of transposition

  16. Science. 1991 Sep 6;253(5024):1125-8Possible horizontal transfer of Drosophila genes by the mite Proctolaelaps regalis.Houck MA, Clark JB, Peterson KR, Kidwell MG. D. willistoni The P element took a ride on a ~50 yrs ago That moved it onto Mite D. melanogaster

  17. Retrotransposons mRNA DNA

  18. Examples of retrotransposons elements Yeast • Ty • Copia • Alu Drosophila Humans

  19. General Mechanism Of Retrotransposons Note: retrotransposons are not found in prokaryotes

  20. Types of Retrotransposons Humans • Alu Non-Viral • Ty • Copia Yeast Viral Drosophila

  21. Non-viral Retrotransposons Humans Non-Viral SINES LINES Example: Line 1 and Line 2 Alu

  22. ALU • 300 bp • Endonuclease cutting site: site5' AG/CT 3‘ • Retrotransposon • 1 million in genome • Linked to variety of disorders

  23. Alu has inserted in NF-1 gene Neurofibromatosis: autosomal dominant Growth of nodules mainly affecting nerves in the skin

  24. Viral retrotransposons look a little like retroviruses—but are NOT the same !

  25. Now we must compare a Viral RNA with a Viral Retrotransposon

  26. VIRAL RNA

  27. Infectious process

  28. Now a viral retrotransposon

  29. Here’s the Copia element of Drosophila Similar gag and pol sequences Compare to the retrovirus

  30. Here’s the Ty element, again notice similarities to retroviruses Delta sequences function like LTR’s in viruses

  31. Summary Table Ty and Copia viral retrotransposons Viral and non-viral Alu non viral retrotransposons

  32. A topic of scientific discussion is what is a “prion”?

  33. Blunt cut from donor

  34. HUMAN IMMUNODEFICIENCY VIRUS Human Helper T Lymphocyte

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