AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
The genetic material is not enclosed in a nucleus.
Full specification wording
Eukaryotes and prokaryotes: The genetic material is not enclosed in a nucleus.
In a bacterium the genetic material is DNA, but it is not wrapped in a nuclear membrane.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 4 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
In a bacterium the genetic material is DNA, but it is not wrapped in a nuclear membrane. Instead the main circular DNA molecule sits free in the cytoplasm, usually as a single loop called the bacterial chromosome. Many bacteria also carry small circular plasmids, which are separate from the main loop and can be passed between cells. Because there is no nucleus, the DNA is in direct contact with the cytoplasm, so transcription and translation can happen at the same time and place. This is a key difference from eukaryotic cells, where the nucleus separates DNA from the cytoplasm. When comparing, state both sides: eukaryotic DNA is enclosed in a nucleus, while prokaryotic DNA lies free in the cytoplasm.
What earns the marks
- States that bacterial genetic material is DNA.
- States that the DNA is not enclosed in a nuclear membrane.
- Describes the main DNA as a circular loop or chromosome lying free in the cytoplasm.
- Names plasmids as small additional circular DNA molecules.
- Contrasts this with eukaryotic cells, where DNA is enclosed in a nucleus.
- Links the absence of a nucleus to DNA being in direct contact with the cytoplasm.
Common mistakes and how to put them right
Saying bacteria have no genetic material.
Put it right by stating that they have DNA but no nucleus around it.
Describing bacterial DNA as linear.
Put it right by calling the main molecule circular.
Confusing plasmids with the main chromosome.
Put it right by describing plasmids as small extra circles that are not the main genetic material.
Exam tips
- Write both halves of a comparison, for example eukaryotic DNA is enclosed in a nucleus whereas prokaryotic DNA is not.
- Use the word circular when describing bacterial DNA, and mention plasmids only if the question asks about extra DNA.
- Avoid saying bacteria have no nucleus membrane without also saying where the DNA actually is.
Try the lesson
The start of the Eukaryotes and prokaryotes: The genetic material is not enclosed in a nucleus. lesson, made from checked teaching notes for this specification point.
Have a go first
Where is the genetic material found in a bacterial cell?
Listen
In a bacterium the genetic material is DNA, but it is not wrapped in a nuclear membrane. Instead the main circular DNA molecule sits free in the cytoplasm, usually as a single loop called the bacterial chromosome. Many bacteria also carry small circular plasmids, which are separate from the main loop and can be passed between cells. Because there is no nucleus, the DNA is in direct contact with the cytoplasm, so transcription and translation can happen at the same time and place. This is a key difference from eukaryotic cells, where the nucleus separates DNA from the cytoplasm. When comparing, state both sides: eukaryotic DNA is enclosed in a nucleus, while prokaryotic DNA lies free in the cytoplasm. A strong answer earns marks for these points. States that bacterial genetic material is DNA. States that the DNA is not enclosed in a nuclear membrane. Describes the main DNA as a circular loop or chromosome lying free in the cytoplasm. Names plasmids as small additional circular DNA molecules. A common slip: Saying bacteria have no genetic material. Instead, stating that they have DNA but no nucleus around it. Exam tip: Write both halves of a comparison, for example eukaryotic DNA is enclosed in a nucleus whereas prokaryotic DNA is not.
See it
Key words
Say what each word means before you turn the card.
Bacterial chromosome
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Plasmids
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Eukaryotic DNA
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Prokaryotic DNA
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See every definition
- Bacterial chromosome
- The main circular DNA molecule that sits free in the cytoplasm, usually as a single loop.
- Plasmids
- Small circular DNA molecules that are separate from the main loop and can be passed between cells.
- Eukaryotic DNA
- Genetic material that is enclosed in a nucleus, which separates the DNA from the cytoplasm.
- Prokaryotic DNA
- Genetic material that is not enclosed in a nuclear membrane and lies free in the cytoplasm.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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