Question

1- A miRNA regulates its target mRNA by degradation. Let’s assume the target mRNA has an arbitrary expression level of 1. When you overexpress the miRNA 5-fold, what is the expression level of the target mRNA?

2- You have made iPSCs from a mouse of the Sv129 strain and are now injecting some of them into a skin fold on the back of a Sv129 mouse. A teratoma forms that is about 20 mm3 in volume. You are also injecting the same number of cells intoC57BL6 mice and SCID mice. How do the teratomas differ?

3- After you have done that experiment, you also want to test iPSCs that you have made from fibroblasts harvested from your own skin. Which of the above mouse models would you choose and why?

4- You have isolated Sv129 embryonic stem cells and have tried a new culture condition to keep them pluripotent. To test for the success of your culture protocol, you are injecting the cells into a SV129 blastocyst. Once the pups are born, you notice that your experiment failed. Why did it fail?

5- You are a new Graduate student and have been charged with the task to figure out how to differentiate an embryonic stem cell into a dopaminergic neuron. You are given the choice between using mouse and human embryonic stem cells. Only with regard to culture conditions, which one would you choose and why?

6- Embryonic stem cells are routinely cultured in a medium containing 25 mM glucose. You have ordered medium, because you had run out, but you notice that you have accidentally ordered medium without any glucose in it. So, now you need to add it yourself and your supervisor tells you to make 5ml of a 5 M stock solution of glucose.

C. How much glucose powder do you weigh in?

D. How much of the 5M stock solution are you adding to 500 mL of medium?

Answer 1

Answer :

1. You would see a 5- fold down regulation in mRNA due to the increase in miRNA, since miRNA binds to the target mRNA post- transcriptionally to degrade it.

2. A teratoma is type of tumor that derives its tissue or organ components from more than one germ layer. The specific factors causing iPSCs to become a teratoma stem from the type of PSC being injected, in which number, and the mode of delivery that it used. Meaning if those three factors are held constant in the other mice, there is a good chance the same type of teratoma would develop in other mice.

3. Choosing the SCID mouse would be the best model because it lacks both T- and B- lymphocytes meaning it would not have an immune response and thus would be less likely to reject the injected iPSCs.