Summary AQA A level biology flashcards the control of gene expression chapter 20
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Course
Unit 7 - The control of gene expression
Institution
AQA
Here are some A-level biology AQA flashcards that I made before exams using information from Miss Estruch's videos as well as the textbook. I have used both these sources to ensure that I do not miss out even the tiniest piece of information in my notes. These question flashcards have really worked...
1.What is a gene mutation?
● A change in the DNA base sequence of a gene
2.what happens if a gene mutation occurs?
● Result in a different amino acid sequence in primary structure
● This causes H and ionic bonds to form in different places
● Resulting in a different tertiary structure with a different shape→ results in non
functioning protein/ different function
3. What is an addition mutation?
● One extra base is added to sequence
● Effect: frameshift occurs, altered codons code for different
AA + result in different sequence of
AA—> resulting in a non- functioning protein
4. What is a deletion mutation?
● When base is deleted in a sequence
● Effect: causes frameshift, results in a different polypeptide chain
+ non- functioning protein
5. What is a substitution mutation?
● One base is changed for a different base
● Effect: only 1 codon changes + due to genetic code being
degenerate, it may still code for same AA + have no impact
6. What is an inversion mutation?
● Group of bases separated + rejoined in reverse order
● Impact: codes for a different AA + results in different primary
structure
7. What is a duplication mutation?
● 1 or more bases are repeated
● Impact: causes frameshift + different sequence of AA is coded
for, so different primary structure produced
8. What is a translocation mutation?
● Section of bases on 1 chromosome detaches + attaches onto different chromosome
● Impact: Can affect multiple proteins + cause frameshift in multiple locations + result in a
different phenotype
9.what is the mutation rate increased by?
● Mutagenic agents- high energy ionising radiation disrupts the DNA molecule, chemicals
such as nitrogen dioxide alter DNA structure or interfere with transcription
, 10.what are the causes of mutation:
● Spontaneous error during DNA replication
● Chemical mutagens- benzene, alcohol, asbestos, tobacco
● Ionising radiation- UV, X-ray, alpha, beta
Stem cells
1.Totipotent stem cells
● Can divide + produce any type of body cell
● Occur only for a limited time in early mammalian embryos
● During development, totipotent cells can only translate part of their DNA (only certain
genes are switched on)----> RESULTS IN DIFFERENTIATION/SPECIALISATION
2.Pluripotent stem cells
● Found in embryos
● Can divide into unlimited numbers + differentiate into almost any type of cell
● Used in treating human disorders (e.g. regrowth of damaged skin cells)
3.multipotent stem cells:
● Found in mature mammals- adults cells
● Can differentiate into a limited number of cells
● Ex: bone marrow is multipotent stem cells + can only make blood cells
4.unipotent stem cells:
● Found in mature mammals- adults cells
● Can only differentiate into 1 type of cell
● EX: used to make cardiomyocytes
5.what are the issues surrounding pluripotent stem cells?
● Stem cells can continue to divide, producing a tumour
● Ethical problems- destruction of embryo
6.what are induced pluripotent cells created from?
● Adult unipotent cells (somatic)
7.how can induced pluripotent cells be produced from adult somatic cells?
● Treated with transcription factors
● The genes that were switched off to make the cell specialised must be switched back
on→ uses transcription factors to do this
8. What are the advantages of induced pluripotent cells?
● Does not destroy embryos- so no ethical issues
● Self- renewal property, so can divide indefinitely + be used for a long time
● Used in medical treatment instead of embryonic stem cells
● Produced from adult somatic cells (patient), so no risk of rejection
9.how do transcriptional factors work?
● Attach to gene/DNA/ promoter region
● Stimulate/inhibit transcription
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