1. What is a microRNA (miRNA)? How can they affect gene expression (at mRNA leve

Question

1. What is a microRNA (miRNA)? How can they affect gene expression (at mRNA level and at translation level)?

2. What are the typical protein processing steps to make them active after the polypeptides are translated? Is insulin active immediately after its synthesized?

3. What does signal transduction do? What molecules participate in this process? Where these molecules are usually located? What are the common cellular responses to the signal transduction pathways?

4. What technologies can help you detect gene expression in small scale of some genes and in large scale of thousands of genes? What is DNA microarray?

5. What effects does cell differentiation have in gene expression? Can terminally differentiated plant cells retain totipotent in normal cell culture? Is cloning sexual or asexual reproduction?

6. What technology is needed for animal cloning? What is called the aggregate of cell mass that can be transferred to the surrogate mother to give birth of the cloned the animal? What traits or phenotypes would a cloned animal show, the donor of the nucleus, or the donor of the eggs, or the surrogate mother animal?

7. What is the difference of reproductive cloning and therapeutic cloning? What cells are needed for therapeutic cloning? What source do these cells come from? Where can you find adult stem cells? Are adult stem cells totipotent?

8. What is a proto-oncogene? What type of mutations on proto-oncogene promote tumor progression?

9. What is a tumor-suppressor gene? What type of mutation of such genes promote tumor progression?

10. Are cancers usually inheritable? And why?

11. What is a carcinogen? Give some examples of carcinogens. How would healthy life style help fight against cancer?

12. What is gene cloning? What DNA segments are needed in the recombinant DNA technology?

13. What enzymes can be used to manipulate DNA segments in DNA recombination?

Explanation / Answer

Ans1:

miRNA refers to micro RNA which are non coding RNA molecules. This means that they do not code for any protein (thus do not undergo translation).

However, they play important role in transcription and translation.

They bind to 3' end of mRNA and destabilise them. This stops transcription. They act this in conjugation with RISC complex, where miRNA plays role of guide molecule and recognising which mRNA to silence.

This ultimately represses translation (as mRNA becomes non functional).

Ans2:

Mechanisms to activate a protein:

Insulin is activated by cleavage of a short peptide from within the inactive insulin polypeptide, then the two fragments are joined to form active insulin.

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