2. The -10 core promoter of the lac operon gene has the sequence TATGTT. Describe an...

2. The -10 core promoter of the lac operon gene has the sequence TATGTT. Describe an example of a base substitution mutation which would lead to increase transcription of the gene. Explain whether this mutation would increase or decrease the fitness of the organisms.

Solutions

Expert Solution

The lac promoter is not a particularly strong promoter, and mutations have been obtained that either increase or decrease its efficiency of initiating transcription. The given -10 promoter sequence is TATGTT is not a strong promoter and therefore Base substitutions(G to A) will make the promoter sequence more similar to the consensus sequence (TATATT) which will generate a stronger promoter (promoter "up" mutations). An "up" mutation would make the lac operon no longer dependent on the positive regulation by the cAMP?CAP complex (when the operon is induced) and will show an inducible phenotype.

E.coli has about 4500 genes. Some genes are constitutively expressd or some genes are expressed only under certain conditions. Because of Base substitution (transition from G to A), the promotor becomes a strong one and regulate transcription more strongly even in harsh environment thereby increasing transcription.This ability to regulate gene in harsh environment is ADAPTATION- increasing fitness.

gladiator answered 1 year ago

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