Prokaryotic DNA (AQA A Level Biology)

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

Image showing the arrangement of DNA within a prokaryotic cell