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Summary A* Gene Expression notes
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A* Gene Expression notes
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Gene expression:(Other types of mutation) Addition of bases:
Extra bases become inserted, the effect is similar to deletion as it causes a frame shift, but to the
right
Duplication of bases:
One or more bases are repeated, causing a frame shift to the right
Inversion of bases:
Group of bases become separated and re-join in the reverse order so the amino acid coded for may
change
Translocation of bases:
Group of bases move from one chromosome to another, causing significant effects on gene
expression, leading to an abnormal phenotype
Causes of mutation:
Spontaneously, permanent changes happen during DNA replication- no outside influence
How is basic mutation rate increased?
Mutagenic agents- high energy radiation disrupts DNA molecule and chemicals that alter DNA
structure interfere with transcription
What is the benefit of this?
Mutations produce genetic diversity necessary for natural selection and speciation
What is the drawback to this?
Make the individual less suited to the environment i.e., death
How does differentiation work?
Some genes are permanently switched on/off so only certain genes are expressed at any one time
Give the definition of differentiation?
The process of turning on/off different genes to perform different functions
Give an example of genes switched on?
Respiration enzymes
Give an example of genes switched off?
Insulin genes in the intestine
What are stem cells?
Differentiation is irreversible in most animals, but stem cells retain the ability to divide, they are
undifferentiated dividing cells
, Where do they occur?
In adult tissues
What do they need to be?
Constantly replaced (cell division= cell renewal)
What is totipotency?
Found in early embryos and can differentiate into any type of cell
What is pluripotency?
Found in early embryos and can differentiate into almost any type of cell
What is multipotency?
Found in adults and can differentiate into a limited number of cells
What is unipotency?
Made in adult tissues and can only differentiate into one type of cell
Source of stem cells in mammals
Embryonic stem cells (pluripotent), placenta stem cells (unipotent), adult stem cells (multipotent and
specific to tissues with a role of maintenance and repair)
What are induced pluripotent cells?
Produced from a unipotent cell so a specialised cell produced from an embryonic stem cell in a lab
using transcriptional factors to genetically alter the cell
Give characteristics of induced pluripotent cells?
Similar to embryonic stem cells, can self-renew and can potentially provide a limitless supply of cells
Reasons for the use of embryos in stem cell research?
Cure disease, prevent suffering, IVF uses embryos and less than 14 days old
Reasons against the use of embryos in stem cell research?
Embryos are potential humans, have human genes, slippery slope and adult stem cells are an
alternative
How do cells turn off and on genes?
1- prevent transcription of mRNA
2- breaking down the mRNA before it can be translated
How is transcription started?
A gene is stimulated by a specific molecule travelling from the cytoplasm into the nucleus called
transcriptional factors
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