1a. which is likely to be more deleterious, a 1bp deletion from an exon in the c

Question

1a. which is likely to be more deleterious, a 1bp deletion from an exon in the coding sequence of a gene, or a 3 bp deletion? Explain clearly what all the potential consequences of both deletions could be on the proteins amino acid sequence.

1b. how many different 9-nucleotide mRNA sequences could you make that would produce the peptide tyrosine-leucine-arginine? Assume you are using a cell-free system that does not require a START codon.

1c. imagine you have a single nucleotide substitution (an A has mutated to a G, for example) in an exon of a gene's coding region. It reduces the activity of that gene's protein in your cells to 50% of the usual level of activity. Imagine also that you have a single nucleotide substitution in the same gene's promoter region, and this mutation also reduces the activity of that gene's protein in your cells to 50% of the usual level of activity. Do the 2 mutations reduce the proteins activity level via the same mechanism? Explain your answer.

Explanation / Answer

1A)

I believe the 1bp deletion from the exon would be more deleterious as this would result in a frame shift which would result in a completely different aminoacid sequence from the changed sequence. This happens because ribosome reads the genetic sequence in pairs of 3 so deleting a single bp would completely change what the ribosome recognises now. On the other hand deleting 3 basepairs would eleminate1 or at most 2 aminoacid in a polypeptide chain so that might not have much effect on the function of the protein as the frame will still be in place.

1B)

tyrosine is coded by 2 codons, leucine by 6 codon and arginine by 6 as well. so the possible combinations are 2x6x6 = 72.

1C)

No, the mechanism to change the activity would be different since change is exon is ultimately represented in change in a single amino acid sequence that might be present in the active site of the protein to which it belongs. So change in the active site changes the effeciency of the enzyme.

The change in promoter region would mean that the proteins that are binding to that specific promoter are no longer able to bind with the previous effeciency so the number of sucessfull attempts on transcribing the sequence are reduced due to which the amount of protein is reduced and so the activity is reduced.

Feel free to leave a comment down below for any further query. Good rating would be appretiated if you find my answer helpful. Thank you.

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