AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Binary fission in prokaryotic cells involves: replication of the circular…
Full specification wording
All cells arise from other cells: Binary fission in prokaryotic cells involves: replication of the circular DNA and of plasmids division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
Prokaryotes divide by binary fission, not by the eukaryotic cell cycle.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 12 of 14
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Prokaryotes divide by binary fission, not by the eukaryotic cell cycle. The single circular DNA molecule is replicated, and plasmids replicate separately and independently, so their copy number is controlled by plasmid-encoded mechanisms rather than by the host cycle. The two circular DNA copies attach to the cell-surface membrane at opposite ends as the cell elongates, and the cytoplasm divides, with a new cell wall forming across the middle, giving two daughter cells. Each daughter normally receives one copy of the circular DNA but a variable number of plasmids, because plasmid segregation is not perfectly equal; this is why plasmid-borne antibiotic resistance can be distributed unevenly between descendants. There is no spindle, no nuclear envelope to break down and reform, and no histone-wound chromosomes, because there is no nucleus.
What earns the marks
- Replication of the circular DNA, with plasmids replicated separately and independently of it.
- Division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA.
- Each daughter cell receives a variable number of plasmid copies, because plasmid segregation is not perfectly equal.
- Binary fission occurs in prokaryotes and contrasts with the eukaryotic cell cycle, in which DNA replication happens in interphase (S phase) and mitosis is the nuclear division that separates the replicated linear DNA.
- No spindle forms and no nuclear envelope breaks down, because prokaryotes have no nucleus; the circular DNA is not wound around histones.
Common mistakes and how to put them right
Writing that binary fission involves mitosis, a spindle, or chromosomes lining up on an equator.
Put it right: Binary fission has none of these; mitosis is nuclear division in eukaryotes.
Saying each daughter cell receives an identical number of plasmids.
Put it right: Plasmid number is variable because segregation is not perfectly equal.
Confusing binary fission with meiosis and claiming four daughter cells.
Put it right: Binary fission produces two daughter cells.
Describing the circular DNA as a chromosome without qualification.
Put it right: The specification refers to circular DNA, so use that term.
Stating that DNA replication occurs during mitosis.
Put it right: Replication occurs in interphase (S phase); mitosis separates the already-replicated DNA.
Exam tips
- In a comparison table, replication of circular DNA and no spindle belong to binary fission; replication of linear DNA in interphase and spindle formation in mitosis belong to the eukaryotic cell cycle; two daughter cells applies to both.
- Use the word variable about plasmid number; it is the detail the specification singles out.
- Do not describe stages by name; binary fission has none, so a staged answer signals you have imported mitosis.
Try the lesson
The start of the All cells arise from other cells: Binary fission in prokaryotic cells involves: replication of the circular DNA and of plasmids division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids. lesson, made from checked teaching notes for this specification point.
Have a go first
Which process do prokaryotic cells use to divide and produce two daughter cells?
Listen
Prokaryotes divide by binary fission, not by the eukaryotic cell cycle. The single circular DNA molecule is replicated, and plasmids replicate separately and independently, so their copy number is controlled by plasmid-encoded mechanisms rather than by the host cycle. The two circular DNA copies attach to the cell-surface membrane at opposite ends as the cell elongates, and the cytoplasm divides, with a new cell wall forming across the middle, giving two daughter cells. Each daughter normally receives one copy of the circular DNA but a variable number of plasmids, because plasmid segregation is not perfectly equal; this is why plasmid-borne antibiotic resistance can be distributed unevenly between descendants. There is no spindle, no nuclear envelope to break down and reform, and no histone-wound chromosomes, because there is no nucleus. A strong answer earns marks for these points. Replication of the circular DNA, with plasmids replicated separately and independently of it. Division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA. Each daughter cell receives a variable number of plasmid copies, because plasmid segregation is not perfectly equal. Binary fission occurs in prokaryotes and contrasts with the eukaryotic cell cycle, in which DNA replication happens in interphase (S phase) and mitosis is the nuclear division that separates the replicated linear DNA. A common slip: Writing that binary fission involves mitosis, a spindle, or chromosomes lining up on an equator. Instead, binary fission has none of these; mitosis is nuclear division in eukaryotes. Exam tip: In a comparison table, replication of circular DNA and no spindle belong to binary fission; replication of linear DNA in interphase and spindle formation in mitosis belong to the eukaryotic cell cycle; two daughter cells applies to both.
Key words
Say what each word means before you turn the card.
circular DNA replication
Try answering aloud or in your head before turning the card.
independent plasmid replication
Try answering aloud or in your head before turning the card.
variable plasmid number
Try answering aloud or in your head before turning the card.
no spindle and no nucleus
Try answering aloud or in your head before turning the card.
See every definition
- circular DNA replication
- The single circular DNA molecule is replicated, and the two circular DNA copies attach to the cell-surface membrane at opposite ends as the cell elongates.
- independent plasmid replication
- Plasmids replicate separately and independently, so their copy number is controlled by plasmid-encoded mechanisms rather than by the host cycle.
- variable plasmid number
- Each daughter cell receives a variable number of plasmid copies, because plasmid segregation is not perfectly equal.
- no spindle and no nucleus
- No spindle forms and no nuclear envelope breaks down, because prokaryotes have no nucleus; the circular DNA is not wound around histones.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of All cells arise from other cells: Binary fission in prokaryotic cells involves: replication of the circular DNA and of plasmids division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge