8) Is an example of a Dominant Negative mutation a) lac b) lacl c) lac d) lac? e

Question

8) Is an example of a Dominant Negative mutation a) lac b) lacl c) lac d) lac? e) Promoter up mutations f) Promoter down mutations g) b and c h) e and f 9) Which is not true concerning operon polarity a) cannot occur in eukaryotes b) requires coupling of transcription and translation c) results in the non-expression of downstream genes in an operon d) results in the formation of translational termination stem loop structures e) causes the formation of premature stop codons f) can be suppressed by certain tRNA mutations g) none of the above

Explanation / Answer

Ans.

8)- d

lac Oc is an example of dominant negative mutation as this mutation inactivates the operator site . so, in merodiploids there is constitutive expression regardless of the presence or absence of the inducer.

9) - d

Operon polarity is a failure to express downstream genes in an operon due to a mutation located upstream in the operon.it can be due to targeted mutations in the upstream gene causing premature translational termination. however it does not results in the formation of translational termination stem loop structures.

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