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Mutants: Each of the above four codes represent a mutation to the original code. Try and identify which is which.
Impact of mutation (protein folding/cancer):
Mutation can cause many different consequences, or often none at all.
-It must first be noted that mutation can affect how a protein folds and is translated- remember that the primary sequence (the sequence of AA) determines the secondary and tertiary structure of a protein. Even single changes made to this sequence can cause mis functional proteins (enzymes, receptors) to be coded for.
-It must also be recognised that mutation can have no effect on the synthesis of the protein (the idea that the same/a similar AA is coded for by the mutation) and therefore mutation can often have no effect at all.
-Mutations in genes which control cell division and growth can lead to cancer- the idea that mutations to genes controlling cell division will cause uncontrollable cell division to occur- cancer.
Coronavirus Mutations: E484K
The Kent variant shows a mutation at amino acid number 484. At the position, an EK substitution mutation has occurred, meaning that glutamic acid has been mutated to lysine.
E (glutamic acid) = negative charge
K (lysine) = positive charge
This change in charge in the spike domain of the virus may be responsible for increased transmissibility.
Substitution Mutation: A base in the code is simply swapped for a different base. For example A-G would be a substitution mutation. This can be silent or non-silent, as the resulting mutation can cause a different AA to be coded for by the triplet codon, or the same AA. This is because of the degenerate nature of the genetic code.
Deletion Mutation: A base in the code is removed altogether. This can be highly influential on the resulting polypeptide. Deletion causes frameshift to occur (the whole code's reading frame is displaced by 1) and therefore any triplet codon following the deletion mutation can be altered. This can cause improper protein folding, early STOP codons (truncation) or a completely different protein altogether.
Addition Mutation: A base in the code is added. This can be highly influential on the resulting polypeptide. Addition also causes frameshift to occur (the whole code's reading frame is displaced by 1) and therefore any triplet codon following the addition mutation can be altered. This can cause improper protein folding, early STOP codons (truncation) or a completely different protein altogether to be coded for.
Inversion Mutation: A region of the base code is inverted. For example, a triplet codon reading AUG (START) could be mutated to GUA. This can cause a single amino acid to be changed, leading to a discrepancy of 1 with regard to the correct sequence of amino acids. This, much like the substitution mutation, can be silent or non-silent.
Causes of mutation & mutagenic agents:
-Exposure to UV radiation can cause mutations to arise, sometimes through the fusion of bases or damage to bases.
-Benzopyrenes are mutagenic agents (chemicals which induce mutation) found in cigarette smoke. These chemicals intercalate in between DNA bases and distort the DNA, mutating it as it does so.
-Damage to cells can even cause mutation. Cancer cells typically respond in a similar way to wounded cells, secreting signals which stimulate the growth of blood vessels into the tumour (angiogenesis). This supplies the cancer with its own private supply of oxygen and glucose for the high metabolic demand cancer cells have.
-Cancers arise due to mutations in genes controlling cell division and growth.
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