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Types of DNA in Genomes - Techniques in Molecular Biology - Lecture Slides, Slides of Cellular and Molecular Biology

Types of DNA in Genomes, Coding Regions, Repetitious Elements, Mobile DNA Elements, RNA Transposable Elements, DNA Transposons, Mechanism of Transposon Action, Eukaryotic Genomes. Enjoy about Techniques in Molecular Biology from this lecture handout.

Typology: Slides

2011/2012

Uploaded on 12/23/2012

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Types of DNA in genomes
Genes (coding regions)-nonrepetitive
Prokaryotes and simpler eukaryotes: densely packed
More complicated eukaryotes: regions of coding and noncoding regions
Repetitious elements: Noncoding regions
Highly repetitive
Satellite
Minisatellite
Microsatellite
Moderately repetitive
Mobile DNA elements
DNA transposable elements (DNA transposons)-Class II
RNA transposable elements (retroposons)-Class I
Other elements
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Types of DNA in genomes

  • Genes (coding regions)-nonrepetitive
    • Prokaryotes and simpler eukaryotes: densely packed
    • More complicated eukaryotes: regions of coding and noncoding regions
  • Repetitious elements: Noncoding regions
    • Highly repetitive
      • Satellite
      • Minisatellite
      • Microsatellite
    • Moderately repetitive
      • Mobile DNA elements
        • DNA transposable elements (DNA transposons)-Class II
        • RNA transposable elements (retroposons)-Class I
  • Other elements

Figure 1 : The relative amount of retrotransposons and DNA transposons in diverse eukaryotic genomes. Species abbreviations: Sc: Saccharomyces cerevisiae; Sp: Schizosaccharomyces pombe; Hs: Homo sapiens; Mm: Mus musculus; Os: Oryza sativa; Ce: Caenorhabditis elegans; Dm: Drosophila melanogaster; Ag: Anopheles gambiae, malaria mosquito; Aa: Aedes aegypti, yellow fever mosquito; Eh: Entamoeba histolytica; Ei: Entamoeba invadens; Tv: Trichomonas vaginalis. From Nature Scitable 1(1): 2008

RNA transposable elements

  • Derived from an RNA intermediate
  • Seen only in eukaryotic genomes
  • Originated from ancient retroviral genome
    • Retrotransposon
      • LTR elements
    • Retroposons
      • SINE-human
      • LINE-human
  • Derived from a viral genome from the

retrovirus:

LTR (^) gag RT env LTR

RT: reverse transcriptase^ ~7 kb LTR: long terminal repeat gag, env: encode proteins needed for retroviral assembly and infection

Retroelements: missing some or most of the complete retroviral genome;

Human Retroposons: non-LTR

  • LINE: long interspersed elements

~6 kb

gag? RT^ poly(A)

  • SINE: short interspersed element;

The Alu element is a well known example

~0.3 kb

poly(A)

Other types of elements

  • Pseudogenes : predominantly eukaryotic;

represent sequences that resemble genes (exons,

introns) but over time accumulated mutations

that prevent production of either RNA or protein

  • Can be repeated in genomes
  • Controversy on whether they are “functional” or not
  • Spacer DNA : DNA which has not been classified

into the other categories