# Tutor profile: Joanna B.

## Questions

### Subject: Pre-Algebra

Frankie plans to make 25 apple pies for a bake sale. The recipe calls for 5 apples per pie. If apples at the grocery store are sold by the dozen, what is the least number of apple bundles that Frankie must buy?

First, we use multiplication to determine the total number of apples that Frankie needs. Frankie is making 25 apple pies and each pie requires 5 apples. So, Frankie needs 25 x 5 = 125 apples. Next, we use division to figure out how many dozens are in 125. 125 apples is about 125/ 12= 10.42 dozen apples. Since Frankie can't buy 0.4 dozen, we have to round up to the nearest whole number so that Frankie has enough apples, which is 11 dozen apples. 11 x 12 = 132 apples. So, Frankie must buy 132 apples.

### Subject: Basic Math

A test has 20 questions. If Joanna gets 70% correct, how many questions did Joanna miss?

The number of correct answers is 70% of 20 or 70/100 x 20 = 0.7 x 20 = 14. Since the test has 20 questions and she got 14 correct answers, the number of questions she missed is 20 - 14 = 6. So, Joanna missed 6 questions on the test.

### Subject: Biology

Describe the epigenetic mechanisms responsible for the association between maternal care and stress response in rat pups.

In rat pups, the level of maternal care affects the transcription of glucocorticoid receptors (GRs) in the hippocampus, which is an important site for negative feedback (of cortisol). These GRs are thus necessary for the proper regulation of the HPA axis, as they mediate negative feedback. Mineral corticoid receptors (MRs) respond to cortisol at baseline levels. These MRs become saturated when cortisol levels are high (during stress) and continue to rise because all of the MRs are occupied. Once this saturation point is reached, the GRs are activated by the abundance of cortisol that isn’t sequestered by the MRs, and it is the GRs that mediate the negative feedback loop of cortisol. They act to restore the baseline cortisol levels. However, with the lack of GRs, negative feedback does not work as well and cortisol levels remain high. In rats, a low level of early care reduces the expression of GRs due to their methylation, which leads to reduced sensitivity of the hippocampus to corticosteroids in adulthood. The lack of negative feedback results in heightened and prolonged cortisol elevation during the stress response.

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