The control of gene expression Flashcards
Mutation
Trigger words
- Quantity
The change to the quantity or the structure of the DNA of the organism.
Gene mutation
Nucleotides
Including change to one or more nucleotide bases or any rearrangement of the bases in DNA.
Substitution of bases
Trigger words
- Replacement
- Section
A type of gene mutation in which a nucleotide in a section of the DNA moleucle is replaced by another nucleotide that has a different base.
What are Additon and deletion mutations?
Trigger Words:
- Inserted
- Deleted
- Nucleotides
Where one or more nucleotides (bases) are either inserted or deleted from the DNA sequene.
What is a duplication mutation?
In the name
Where one or more nucleotides (bases) duplicate and repeat.
What is an inversion mutation?
- Separted
- Reverse
Where a group of nucleotides (bases) become separated from the DNA sequence. Then rejoin in the reverse order i.e they have flipped.
What is a translocation mutaton?
Trigger words
- Seperated
THEN
- Into different ?
Where a group of nucleotides (bases) become separted from the DNA seqence, and are then inserted into the DNA of a different chromosomes.
Which mutations are most likely to have a significant impact and why?
IDDT
Reason =
Frameshift
Meaning?
Entire
- Insersion
- Deletion
- Duplication
- Translocation
Reason = As they produce a frameshift, meaning the entire amino acid sequence produced with be different
Which mutations are less likely to have a significant impact and why?
SI
Reason =
Only alter few
Affected bc nature of code
- Substitution
- Inversion
Reason= As they only alter one or very few triplets, the amino acid sequence might not be affected due to the degenerate nature of the genetic code
Is a mutation resulting in a change to the amino acid sequence always harmful?
Reason ?
Beneficial ?
Trigger words:
resulting Change in…
Natural
No
Reason = may be neutral if the resulting change in protein has no effect on the organism.
Benefical = Which is the basis for evolution and natural selection
What is a muagenic agent. Give examples?
Trigger words.
Increase
A
B
IR
Factors that increase the rate of gene mutation
Example = Chemical muagens such as:
- Alcohol
- benzene
- Ionising radiatyion such as UV and X-ray
Gene Expression
Trigger words
- Instructions
- Functional p
The process by which the instructions in our DNA are converted into a functional product, such as a protein
What is a stem cell?
Trigger words
- Indefinetly
- Specific cell
Undifferentiated cells, that can divide indefinitley and turn into other specific cell types,
What are the three types of stem cells
Totipotent
Pluripotent
Multipotent
Totipotent
- Any type
Can develop into any cell type including the placenta and embryo
Pluripotent
Trigger Words
Excluding
Can develop into any cell type excluding the placenta and embryo
Multipotent
Trigger words
- Few
Can only develop into a few different types of cells
What happens to totipotent cells during embryonic development?
Trigger words:
- Selectively translated
- Some genes
- Differentitae into … to form
- Certain parts of the DNA are selectively translated
- So that only some genes are ‘switched on’
- in order to differentiate the cell into a specific type and form the tissues that make up the foteus.
Give a unique feauture of puripotent cells and the use of this feauture
Trigger words
- Unlimited
- Repaire & ..
They can divide in unlimited numbers and can therefore be used to repair or replace damaged tissue.
What is a unipotent cell? GIve an example
A cell that can only develop into one type of cell. This occurs at the end of specialisation when e cell can only propagate its own type.
Example: Cardiomyocytyes (Heart cells)
Which types of stem cell are found in embryos?
Totipotent and Pluripotent
Multipotent and unipotent cells are only found in mature mammals.
Give some uses of stem cells
Medical therapies e.g
- bone marrow
- Transplants
- Treating blood disorders
Drug testing on artifically grown tissues.
Research e.g
- Formation of organs and embryos.
How are induced pluripotent stems cells prodced?
From mature, fully specialise (somatic) cells. The cell regains capacity to differentiate through the use of proteins, in particular transciption factors
What is a transcripton factor
A protein that controls the transcription of genes so that only certain parts of DNA are expressed. E.g. in order to allow a cell to specialise.
How do transciption factors work?
- Move from the cytoplasm into nucelus.
- Bind to promoter region upstream of target gene.
- Makes it easier or more difficult for RNA polymerase to bind to gene.
- This increases of decreases the rate of transcription
Give an example of a hormone that affects transcrption and explain how it works.
- Sterioid hormones oestrogen diffuses through cell membrane
- Forms hormone-receptor complex with ER α receptor in the cytoplasm.
- Complex enters the nucleus & acts as transcription factor to facillitate binding of RNA polymerase.
What is meant by epigenetics?
A heritable change in gene function without change to the base sequence of DNA.
How does increases methylation of DNA affect gene transcription?
Involves addition of CH3 group to cytosine bases which are next to guanine. Prevents transcription factors from binding. Therefore gene transcription is supressed.
How does descreased acetylation DNA affect gene transcription?
Postively-charged histones are positvely charged bind to negatibely-charged DNA. Decreasing acetylation increases postive charge of histones. Binding become too tight and prevents transcripton factors from accessing the DNA. Therefore gene transcription is supressed.
How might epigenetic changes affect humans?
They can causes disease, either by over activating a gene’s function (such as in cancer) or by supressing it.
Give an application of epigenetics
Treatments of various diseases. Development of ways to reverse epigenetic changes.
Describe the process of RNA interference, including the organisms in which it occurs
RNA molecules act to inhibit gene expression, usually by destroying mRNA so that it cannot be translated. Occurs in eukaryotes and some prokaryotes.
Give some charactertics of benign tumours
- Slow growth
- Defined by clear boundary due to cell adhesion molecules
- Cells retain function an normal shape
- Dont spread easily
- easiy to treat
Give some characteritics of malignant tumours
- Rapid, uncontrollable growth.
- Ill-defined boundary (finger-like projections.)
- Cells do not retain function and often die
- Spreads quickly and easily (Metastasis)
- Difficult to treat
Describe the role of tumour-supressor genes
Code for poteins that control cell divison.
Stopping the cell cyle when damage is detected.
- Involved in programming apoptosis i.e ‘self destruction of cell>”
Explain how tumour-supressor genes a be involved in developing cancer
A mutation in the gene could code for a decreased acetylatin could prevent transcription
Cells will divide unctrollably resulting in a tumour
Describe the role of proto-ocongeness
Control cell dvision: code for proteins that stimuate cell divison.
Explain how proto-oncogenes can be involved in developing cancer.
Muations in the gene could turn it into a permanentl activated oncogene. Descreaed methlayation or increased acetylation can cause exess transcription.
Resulting = In uncontrolled cell division and formation of a tumour.
Explain how abnormal methylation of genes can cause cancer.
Hyper-methalaytion of tumour-supressor genes or oncogenes can impair their function and cause the cell to divide uncontrollably.
Explain how oestrogen can be involved in developing breast cancer.
We already know oestrogen is an activator of RNA polymerase. Therefore in areas of high oestrogen concentration such as adipose tissue in the breasts, cell division can become uncontrolled..
What is the genome?
The complete set of genetic information contained in the cells of organism.
