AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Pluripotent cells are found in embryos; multipotent and unipotent cells…
Full specification wording
Most of a cell’s DNA is not translated (A-level only): Pluripotent cells are found in embryos; multipotent and unipotent cells are found in mature mammals and can divide to form a limited number of different cell types.
Potency describes the range of cell types a stem cell can form.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 4 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Potency describes the range of cell types a stem cell can form. Pluripotent cells occur in embryos; they divide by mitosis and differentiate into almost any body cell, but not extra-embryonic tissues like the placenta. Multipotent and unipotent cells are found in mature mammals. Multipotent cells form a limited range of related cell types. For example, haematopoietic stem cells in bone marrow produce erythrocytes and white blood cells, but not neurones. Unipotent cells are the most restricted, dividing to produce just one cell type, such as epidermal stem cells forming keratinocytes. Restriction occurs because progressively fewer genes remain available for expression, as parts of the genome are epigenetically silenced.
What earns the marks
- Pluripotent cells are found in embryos and can differentiate into almost any type of body cell, but not extra-embryonic tissue such as the placenta.
- Multipotent cells are found in mature mammals and can divide to form a limited number of different cell types, such as bone marrow stem cells forming various blood cells.
- Unipotent cells are found in mature mammals and can divide to form only one specific cell type.
- The restriction of potency is explained by fewer genes remaining available for expression due to epigenetic silencing, rather than the loss of genetic material.
- A comparison of two potency types should state both what each can form and what it cannot.
Common mistakes and how to put them right
Using pluripotent and totipotent interchangeably.
Put it right: Totipotent cells can form a whole organism including extra-embryonic tissues; pluripotent cells cannot.
Claiming multipotent bone marrow cells can form any body cell.
Put it right: They form a limited range of related blood cell types, not neurones or muscle.
Stating that unipotent cells cannot divide.
Put it right: Unipotent cells can still divide by mitosis, but they differentiate into only one specific cell type.
Believing genes are permanently deleted as cells differentiate.
Put it right: Genes are epigenetically silenced (switched off) rather than permanently removed from the genome.
Exam tips
- When comparing potency types, explicitly state what each can form and what it cannot (e.g., pluripotent cells cannot form placenta).
- Use the specification's exact wording 'mature mammals' when describing where multipotent and unipotent cells are found.
Try the lesson
The start of the Most of a cell’s DNA is not translated (A-level only): Pluripotent cells are found in embryos; multipotent and unipotent cells are found in mature mammals and can divide to form a limited number of different cell types. lesson, made from checked teaching notes for this specification point.
Have a go first
Where are pluripotent cells found?
Listen
Potency describes the range of cell types a stem cell can form. Pluripotent cells occur in embryos; they divide by mitosis and differentiate into almost any body cell, but not extra-embryonic tissues like the placenta. Multipotent and unipotent cells are found in mature mammals. Multipotent cells form a limited range of related cell types. For example, haematopoietic stem cells in bone marrow produce erythrocytes and white blood cells, but not neurones. Unipotent cells are the most restricted, dividing to produce just one cell type, such as epidermal stem cells forming keratinocytes. Restriction occurs because progressively fewer genes remain available for expression, as parts of the genome are epigenetically silenced. A strong answer earns marks for these points. Pluripotent cells are found in embryos and can differentiate into almost any type of body cell, but not extra-embryonic tissue such as the placenta. Multipotent cells are found in mature mammals and can divide to form a limited number of different cell types, such as bone marrow stem cells forming various blood cells. Unipotent cells are found in mature mammals and can divide to form only one specific cell type. The restriction of potency is explained by fewer genes remaining available for expression due to epigenetic silencing, rather than the loss of genetic material. A common slip: Using pluripotent and totipotent interchangeably. Instead, Totipotent cells can form a whole organism including extra-embryonic tissues; pluripotent cells cannot. Exam tip: When comparing potency types, explicitly state what each can form and what it cannot (e.g., pluripotent cells cannot form placenta).
Key words
Say what each word means before you turn the card.
pluripotent
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multipotent
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unipotent
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epigenetic silencing
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See every definition
- pluripotent
- Cells found in embryos that divide by mitosis and differentiate into almost any body cell, but not extra-embryonic tissues like the placenta.
- multipotent
- Cells found in mature mammals that can divide to form a limited number of different cell types.
- unipotent
- Cells found in mature mammals that are the most restricted, dividing to produce just one cell type.
- epigenetic silencing
- The process by which parts of the genome are switched off, so progressively fewer genes remain available for expression and potency becomes restricted.
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