Cellular control Flashcards
What are the two main classes of gene mutation?
- Point mutation
2. Indel mutation
What does point mutation mean?
Point mutation is where one of the base nucleotides is altered to another base. Which can cause the amino acid that is produced from the triplet to change.
What are the tree types of point mutation?
- Silent mutation
- Missense mutation
- Nonsense mutation
Describe what a silent mutation is.
A silent mutation is when there is a change in the base triplet but will still code for the same amino acid and therefore will not have an effect.
Describe what a missense mutation is.
A missense mutation is when there is a change in the triplet base sequence but it will code for a different amino acid and change the polypeptide. Can cause issues such as sickle cell anaemia.
Describe what a nonsense mutation is.
Nonsense mutation occurs when the base triplet is altered and becomes a termination triplet or stop codon. This mutation will cause proteins to become shorter and therefore wont work as they are meant to. This can cause the genetic disease Duchenne muscular dystrophy.
What does indel mutation mean?
Is the insertion or deletion of a base nucleotide to the DNA sequence.
What is Deletion?
Deletion is a type of mutation involving the loss of genetic material. It can be small, involving a single missing DNA base pair, or large, involving a piece of a chromosome.
What is Insertion?
A type of genetic change that involves the addition of a segment of DNA. It may be as small as a single base but can vary significantly in size.
What does the term frameshift mean?
Causing a mutation in which a number of nucleotides not divisible by three is inserted or deleted so as to change the reading frame of some triplet codons during genetic translation.
Give an example of a condition that is caused by a frameshift mutation.
Some forms of Thalassaemia, a haemoglobin disorder resulting from frameshift due to deletion
What is the cause of Huntington disease?
Results from an expanding nucleotide repeat. If the number of repeating CAG sequences goes above a certain number, then the person with that genotype will develop the symptoms of Huntington disease later in life.
Explain how mutation may be beneficial.
They lead to new versions of proteins that help organisms adapt to changes in their environment. Beneficial mutations are essential for evolution to occur. They increase an organism’s changes of surviving or reproducing, so they are likely to become more common over time.
Describe how the presence of lactose intolerance induces the production of two enzymes in the bacteria.
A repressor protein is produced by the regulator gene if there is lactose the lactose will bind to the repressor and change its shape so it is unable to bind to the operator and therefor is not blocking the promotor. This means that the when RNA polymerase is produced it can bind to the promotor which then allows transcription and translation to occur for the enzymes. Lactose permease and beta galactose are made.
What are transcription factors?
A protein or non - coding short RNA that bind to DNA to inhibit or activate transcription.
Explain the role of transcription factors in gene expression.
Transcription factors are vital molecules in the control of gene expression, directly controlling when, where and the degree to which genes are expressed. They bind to specific sequences of DNA and control the transcription of DNA into mRNA.
Explain the sequence of events that demonstrate how the removal of introns produces functional mRNA.
- All DNA of a gene is transcribes.
- Primary mRNA is produced.
- The introns are edited out and removed (using endonuclease)
- The remaining mRNA exons are joined together again using endonuclease by slicing. Forming a continuous strand again.
What is post transcription gene regulation?
Post-transcriptional regulation is the control of gene expression at the RNA level. It occurs once the RNA polymerase has been attached to the gene’s promoter and is synthesising the nucleotide sequence.
What is post translational gene regulation?
Post-translational regulation refers to the control of the levels of active protein.
Explain how cAMP acts a second messenger to activate intracellular enzymes to stimulate transcription.
- A signalling molecule binds to the receptor.
- Activation of G protein which activates adenyl cyclase.
- Catalysis of cAMP from ATP.
- cAMP activates protein kinase A
- PKA can phosphorylate cAMP response element binding (CREB) protein - enters the nucleus and acts as a transcription factors.
How does ATP convert into cAMP.
The alpha subunit with GTP binds to cyclase. This converts ATP to cyclic AMP
What is a cAMP molecule?
A secondary messenger released inside cells to activate a response.
What is gene expression?
The transcription of DNA in preparation for translation.
What is a homeotic gene?
Homeotic gene, any of a group of genes that control the pattern of body formation during early embryonic development of organisms.
