What effect would the following mutations have on the expression of the enzyme c

ID: 68801 • Letter: W

Question

What effect would the following mutations have on the expression of the enzyme coding sequences of the tryptophan operon. Select the letter on the right that describes the effect. In all cases, the level of tryptophan is less than needed to bind the trp repressor. (If the first corresponds to B, and the next 3 to C, enter BCCC)

1) mutations in the leader peptide that change the trp codons to leucine codons? A. decrease transcription when trp is low 2) a mutation in region 4 that prevents it from base pairing with region 3? B. never be transcribed 3) a mutation in region 3 that prevents it from base pairing with region 2? (It can still base pair with region 4.) C. be transcribed constitutively 4) a mutation in the leader peptide that changes a glycine codon into a tryptophan codon? D. increase transcription when trp is low

Explanation / Answer

From the given data,

Operon is a functioning unit of genomic DNA (deoxyribonucleic acid), which is a group of genes whose transcription is under the control of a single promoter. Tryptophan is an amino acid, and if it is excessively synthesized by the organism, it controls its transcription through “trp Operon.”

In this, the tryptophan (corepressor) binds to the repressor protein, and makes it get activated. This activated repressor now binds to the operator site, and prevents the binding of RNA polymerase enzyme, there by inhibiting the protein synthesis.

Therefore,

1) Mutations in the leader peptide that change the trp codons to leucine codons results increase transcription when trp is low. Thus, the correct matching option is (D).

2) A mutation in region 4 that prevents it from base pairing with region results constitutive expression. Thus, the correct option is (C).

3) A mutation in region 3 that prevents it from base pairing with region 2 results inhibition of transcription. Thus, the correct option is (B).

4) A mutation in the leader peptide that changes a glycine codon into a tryptophan codon decrease transcription when trp is low. Thus, the correct matching option is (A).

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What effect would the following mutations have on the expression of the enzyme c

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