Question

12. (4) For each of the situations described below: 1) Which process would be primarily affected: RNA Processing, Translation Initiation, Translation Elongation, Translation Termination and 2) Describe the effect/consequence of the change

a) Deletion of a 5’splice site in a pre-mRNA

b) The underlined mutation in the protein-coding region whose reading frame is shown 5’- AUG-CCA-UAU-ACA-3’ 5’- AUG-CCU-UAA-ACA-3’

c) A mutation that removes the Shine-Delgarno sequence

d) A mutation in the tRNA for the amino acid lysine that changes the anticodon sequence from 3′-UUU-5′ to 3′-UAU-5′

Answer 1

12. (4) For each of the situations described below: 1) Which process would be primarily affected: RNA Processing, Translation Initiation, Translation Elongation, Translation Termination and 2) Describe the effect/consequence of the change

a) Deletion of a 5’splice site in a pre-mRNA

Process affected - RNA processing.

Effect - Deletion of 5' splice site will inhibit intron splicing in both spliceosome and self - splicing pathway since spliceosome recognises 5' splice site for RNA binding and 5' splice site initiates intron splicing in self-splicing pathway.

b) The underlined mutation in the protein-coding region whose reading frame is shown 5’- AUG-CCA-UAU-ACA-3’

5’- AUG-CCU-UAA-ACA-3’

Process affected - Translation elongation

Effect - Since UAU codon is converted to UAA which is a stop codon, translation is terminated. Thus elongation doesn't occur.

c) A mutation that removes the Shine-Delgarno sequence

Process affected - Translation initiation

Effect - Shine Delgarno sequence is specifically recognised by ribosomes for mRNA binding. Deletion of SD sequence will result in no translation initiation.

d) A mutation in the tRNA for the amino acid lysine that changes the anticodon sequence from 3′-UUU-5′ to 3′-UAU-5′

Process affected - Translation elongation

Effect - In case of change of anticodon from 3′-UUU-5′ to 3′-UAU-5′, the tRNA will insert Lysine amino acid in place of Isoleucine which is coded by UAU codon. Thus there will be a change in the polypeptide sequence.

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