Question

For each of the following statements concerning regulation of gene expression, choose the single correct answer from the following A-D by typing that letter in the space provided. The choices in A-D may be used once, more than once or not at all.

1. Negative regulation only
2. Positive regulation only
3. Both negative and positive regulation
4. Neither negative nor positive regulation

______ 1. Involves a non-coding sequence.

______ 2. Typically involves strong promoters.

______ 3. Most regulatory mutations result in a constitutive phenotype.

Answer 1

Negative regulation occur when no transcription take place as repressor suppress the transcription of the genes.

Positive regulation occur when efficient transcription take place as repressor cannot suppress the transcription of the gene.

1) neither negative nor positive regulation: non coding sequence does not encode for any functional protein . No regulation is required for non coding sequence.

2) both positive and negative regulation : strong promoter indicate high rate of transcription , if inducer is present positive regulation occur and if inducer is absent negative regulation occur .

3) positive regulation

Constitutive mutations means that gene are constitutively active irrespective of the presence and absence of inducer.