Prokaryotic DNA (AQA A Level Biology): Revision Note

DNA in prokaryotes

• The DNA in prokaryotic cells is different from the DNA found in eukaryotic cells

• 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 which 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