Question

1. Which of the following is NOT a mechanism for gene regulation?

   a. Phase variation in DNA.
2. b. Repressor binding to a promoter.
3. c. Binding of a sRNA to a ribosome-binding site.
4. d. None of the above.

Answer 1

Answer=

1. T he following is NOT a mechanism for gene regulation

2. a. Phase variation in DNA. =

3. Explanation - phase variation is a reversible process that helps bacteria to quickly generate diversity and adpt to rapidly changing environments.One mutation in a 'phase variable'gene can switch expression ON,and another mutation in the same part of DNA will switch the expression of the gene back OFF.

4. therefore is not a mechanism of gene regulation.

5. INCORRECT OPTIONS =

6. regulation of gene is on transcriptional level or translational or post transcriptional level.the all above given are mechanisms for gene regulation.i.e.

   b. Repressor binding to a promoter.- a promoter is a few hundred nucleotides 'upstream' of the gene .it is not transcribed into the mRNA,but plays a role in controlling the transcription of the gene.a repressor is a protein binds to promoter and suppresses its activity therefore further transcription can not occure hence is a mechanism of gene regulation.
7. c. Binding of a sRNA to a ribosome-binding site. = In bacteria,the canonical mechanism of translational repression y small RNAs involves sRNA-mRNA base pairing that occludes the ribosome binding site,directly preventing translation.
8. These 2 are the mechanisms of gene regulation