AQA A Level Biology复习笔记4.1.1 Prokaryotic DNA

• 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