Question

Control of Gene Expression

1. How is it possible that individual cells of a multicellular organisms, which contain all the same DNA, can be so different from one another?

2. What are housekeeping proteins? What are their roles in the cell?

3. Describe the ways in which cells control gene expression.

4. How does control of transcription in prokaryotes and eukaryotes differ?

5. What is the role of operons in the prokaryotic genome?

6. A rare mutation occurs in bacteria that alters the structure of the tryptophan repressor, altering its ability to bind tryptophan. How would this affect the function of the tryptophan operon?

7. A mutation in the 7-pass transmembrane protein causes continued activation of the G-protein responsible for activing a transcription factor that initiates protein synthesis in liver cells. How would this impact protein production in liver cells?

8. Two mRNA molecules have half-lives of 15 min and 1 h, respectively. Which one is more likely to produce more protein? Why?

9. Eukaryotic mRNA translation can be impacted at the 5’ end by preventing the ribosome from finding the start codon. Consider this method of translation control did not exist and was replaced with a region at the 3’ end of the mRNA that inhibits ribosomes from finding the stop codon. What would the cell stand to lose from this system of control?

10. Describe the three types of regulatory RNAs.

11. RNA is single stranded, and as such, undergoes rapid rates of mutation. How would this affect the ability of siRNAs to combat RNA viruses?

12. Long non-coding RNAs aid in formation of Barr bodies. What are Barr bodies and why are they relevant?

13. What role does control of gene expression play in the process of evolution and natural selection?

Answer 1

Answer 1. all cells in an organism have same set of DNA. That means they are also having same set of genes (~20,000 in humans), but the question is how they act differently.

It is because the set of genes work differently in different cells. Each gene has its own time of switching it on or off according the need of different types of cell. For exmaple a neuron cell will express genes which are needed of potential transfer to next neuron, cells in our eyes will express only those genes which are needed to absorb light and give corresponding signal, all other non-needed genes will going to remain off.