Regulation of Gene Expression

1. Regulation of Gene Expression 0 15 Questions prepared by Brad Stith,University of Colorado Denver Louise Paquin,McDaniel College

2. What does the operon model attempt to explain? • the coordinated control of gene expression in bacteria • bacterial resistance to antibiotics • how genes move between homologous regions of DNA • the mechanism of viral attachment to a host cell • horizontal transmission of plant viruses

3. What does the operon model attempt to explain? the coordinated control of gene expression in bacteria bacterial resistance to antibiotics how genes move between homologous regions of DNA the mechanism of viral attachment to a host cell horizontal transmission of plant viruses

4. When tryptophan (an amino acid) is present in the external medium, the bacterium brings in the tryptophan and does not need to make this amino acid. Which is true when there is no tryptophan in the medium? The repressor is active and binds to the operator. The repressor is inactive, and RNA polymerase moves through the operator. The operator is bound, and mRNA is made. Genes are inactive. The corepressor binds to the repressor.

5. When tryptophan (an amino acid) is present in the external medium, the bacterium brings in the tryptophan and does not need to make this amino acid. Which is true when there is no tryptophan in the medium? The repressor is active and binds to the operator. The repressor is inactive, and RNA polymerase moves through the operator. The operator is bound, and mRNA is made. Genes are inactive. The corepressor binds to the repressor.

6. Each of a group of bacterial cells has a mutation in its lac operon. Which of these will make it impossible for the cell to metabolize lactose? mutation in lac (-galactosidase gene) mutation in lac (cannot bind to operator) mutation in operator (cannot bind to repressor) mutation in lac (cannot bind to inducer)

7. Each of a group of bacterial cells has a mutation in its lac operon. Which of these will make it impossible for the cell to metabolize lactose? mutation in lac (-galactosidase gene) mutation in lac (cannot bind to operator) mutation in operator (cannot bind to repressor) mutation in lac (cannot bind to inducer)

8. Which element(s) from the following list constitute(s) a bacterial operon? repressor gene promoter inducer repressor protein all of the above

9. Which element(s) from the following list constitute(s) a bacterial operon? repressor gene promoter inducer repressor protein all of the above

10. General transcription factors in eukaryotes are needed for all genes using the same RNA polymerase. What is the function of specific transcription factors? Of enhancers? How do the enhancers stimulate the transcription initiation complex that is so far away from the enhancers?

11. Approximately what proportion of the DNA in the human genome codes for proteins or functional RNA? 83% 46% 32% 13% 1.5%

12. Approximately what proportion of the DNA in the human genome codes for proteins or functional RNA? 83% 46% 32% 13% 1.5%

13. A specific gene is known to code for three different but related proteins. This could be due to which of the following? premature mRNA degradation alternative RNA splicing use of different enhancers protein degradation differential transport

14. A specific gene is known to code for three different but related proteins. This could be due to which of the following? premature mRNA degradation alternative RNA splicing use of different enhancers protein degradation differential transport

15. RNA is cut up into small 22-nucleotide fragments to regulate another “target” mRNA. Which of the following is/are true? The target mRNA is degraded, and its protein is not made. The RNA fragments enhance protein synthesis by the mRNA. The RNA fragments bind the ribosome to enhance use of the mRNA and protein synthesis. The target mRNA is blocked from being used in translation. The RNA fragments act on the ribosome to shut down translation of all mRNAs.

16. Even though the two cells have numerous transcription factors and many are present in both cells, the lens cell makes the crystallin protein (not albumin), whereas the liver cell makes albumin (not crystallin). Explain (draw the different situation in each cell).

17. Which methods would determine which genes are turned on in a certain cell in an organism? (Choose more than one answer.) Use RT-PCR to identify what mRNAs are present. Use RT-PCR to measure what proteins are present. Use a radioactive probe that binds only to certain mRNAs. Use a fluorescent probe that records DNA replication. Use a fluorescent probe that binds to only certain mRNAs.

18. Which methods would determine which genes are turned on in a certain cell in an organism? (Choose more than one answer.) Use RT-PCR to identify what mRNAs are present. Use RT-PCR to measure what proteins are present. Use a radioactive probe that binds only to certain mRNAs. Use a fluorescent probe that records DNA replication. Use a fluorescent probe that binds to only certain mRNAs.