of 21

Please download to get full document.

View again

All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
21 pages
0 downs
1. Assignment topic: Transposons Subject : Molecular biology LCWU Lahore 2. Transposable Elements DEFINITION ã DNA elements capable of moving ( transposing )…
  • 1. Assignment topic: Transposons Subject : Molecular biology LCWU Lahore
  • 2. Transposable Elements DEFINITION • DNA elements capable of moving ("transposing") about the genome. The movement of genetic information from one chromosomal location, the donor site, to another, the target site.
  • 3. Discovery • Discovered by Barbara McClintock. • Largely from cytogenetic studies in maize, but since found in most organisms. • She liked to call them "controlling elements“ because they affected gene expression. • She got Nobel Prize in 1983 in Physiology and Medicine
  • 4. Genetic Transposition • The ability of genes to change position on chromosomes, a process in which a transposable element is removed from one site and inserted into a second site in the DNA.
  • 5. Mechanism of transposons • Excises the IS element in the donor DNA • Makes staggered cuts in a short sequence in the target DNA • Ligates the three prime termini of the IS element to the five prime ends of the cut donor DNA • Host cell DNA polymerase fills in the single stranded gaps, generating the short direct repeats that flank IS elements and DNA ligase joins the free ends
  • 6. Characteristics • Comprise 45% of human chromosomal DNA “middle repetitive DNA” contribute to spontaneous mutation, • genetic rearrangements, • and horizontal transfer of genetic material. • Aid speciation and genomic change. • In bacteria transposons are often associated with antibiotic resistance genes. • Cells must depress transposition to insure genetic stability.
  • 7. Classification of transposition • Conservative transposition: • The transposable element will only be found at the target site, with no change in copy number. • Also known as “cut-and-paste” transposition.
  • 8. Duplicative transposition: • Will result in two copies of the element, one at the donor site and one at the target site. • copy-and-paste” transposition
  • 9. Types of transposable elements: Class I transposable elements (retro transposons). Class II transposable elements (DNA transposons).
  • 10. Retro transposons: • Retro transposons also called transposons via RNA intermediates are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms.
  • 11. DNA transposons: • DNA fragments transpose directly from DNA segment to DNA segment, Producing a DNA copy that transposes, cut or paste into a new locus. • Insertion sequences: • Also known as an IS, an insertion sequence element, or an IS element is a short DNA sequence that acts as a simple transposable element. • Size: • 700 to 2,500 bp. • Content: • Contain information that required for transposition.
  • 12. Example: Some maize phenotypes caused by transposable elements excising in somatic tissues.
  • 13. BACTERIAL TRANSPOSONS: • In bacteria, transposons can jump from chromosomal DNA to plasmid DNA and back. • Transposons in bacteria usually carry an additional gene for function other than transposition often for antibiotic resistance.
  • 14. Example
  • 15. Control of Transposons: • Auto regulation: • Transcriptional silencing:
  • 16. Transposons causing diseases: • Hemophilia A and B • Severe combined immunodeficiency • Porphyria • Cancer • Duchenne muscular dystrophy.
  • 17. Biological Significance of Transposons: • To identifying the mutant allele. • To study the chemical mutagenesis methods. • To study gene expression • They provide a means for genomic change and variation, particularly in response to stress.
  • Advertisements
    Similar documents
    We Need Your Support
    Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

    Thanks to everyone for your continued support.

    No, Thanks