Prokaryotic DNA and Eukaryotic DNA are essentially the same - a double-helix - but packaged differently.Prokaryotes have one chromosome - a single circular loop of DNA supercoiled around proteins to make it compact.Related genes of prokaryotes are often next to each other, grouped into operons so they can be switched on at the same time.Eukaryotic DNA is supercoiled around scaffold proteins called histones.DNA and histones form a loosely coiled complex called chromatin.Introns are non-coding sequences. Prokaryotic DNA lacks introns.Prokaryotic cells also usually contain one or more small, extrachromosomal loops of DNA called plasmids.
Read the text
Read the text and highlight anything you think is important. When you go on, the text is hidden and you answer from memory.
Specification: OCR Biology A (H020), AS-level, 2.1.1 Cell structure. Topic: Cell Structure.
Key terms in this lesson
- prokaryotic cell
- A cell with no nucleus or membrane-bound organelles, found in bacteria.
- eukaryotic cell
- A cell with a nucleus and membrane-bound organelles, found in animals, plants, fungi and protoctists.
- chromatin
- The complex of DNA loosely coiled around histone proteins found in the nucleus between cell divisions.
- gene
- A length of DNA that codes for a specific polypeptide.
More in Cell Structure
- Cellulose Cell Wall
- Vacuole
- Chloroplasts
- Prokaryotic Cells
- Ribosomes
- Cell Wall
- Flagella
- The Theory of Endosymbiosis
All 26 lessons in Cell Structure · All OCR AS-level Biology topics