AQA AS Biology

Revision Notes

4.1.1 Prokaryotic DNA

DNA in Prokaryotes

  • The DNA in prokaryotic cells is significantly different from the DNA found in eukaryotic cells
  • “Prokaryote” means “before the nucleus”
  • The DNA is double-stranded
  • Prokaryotes possess a single, circular chromosomal DNA molecule
    • It is sometimes referred to as a nucleoid
  • They also usually have one or more plasmids
    • Plasmids are very small circular DNA molecules
    • They usually only contain a few genes
    • Plasmids are more accessible for proteins required for gene expression and therefore contain genes that are required often, quickly and/or in emergencies
    • The genes for antibiotic resistance are often found in plasmids
  • The DNA within prokaryotic cells is not associated with any proteins
    • Eukaryotic DNA associates with histone proteins
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