Compare blood glucose levels after fasting in young control mice and young IKO mice without FoxO1.

Estimate the difference between mean blood glucose levels in control and IKO older female mice.

 .................mg ml^–1
 

Aging and having pregnancies are considered to be physiological stresses.  Deduce the effect of stress on blood glucose levels.

Outline the relationship between blood glucose levels after fasting and lack of FoxO1  in the mice studied.

Calculate the percentage difference in β cell mass of the IKO mice compared to the control mice.

State the correlation between lack of FoxO1 and pancreatic hormones in mice.

Referring to the functions of insulin and glucagon, suggest how the differences in hormone levels help to explain the blood glucose levels.

a. similar/same/nearly same (means)/very small difference/both at a low level;
b. means/averages (all) close to 0.8 mg ml^–1;
c. difference not (statistically) significant;
d. similar/same/nearly same range of values/spread of data;

All marking points are comparisons between control and IKO mice. Do not award marks for comparisons between male and female mice.

1 mg ml^–1 (accept values between 0.8 – 1)

a. stress causes increase in (mean) blood glucose/sugar;
b. older mice/males/females / aging mice show the increase;
Reject answers that only compare control and IKO mice or only compare male and female mice.

a. in young mice/3 month old mice lack of FoxO1/IKO/fewer beta cells does not affect/has little effect on blood glucose/sugar;
b. in older females/aging males blood glucose/sugar (much) higher with lack of FoxO1/IKO/fewer beta cells;

Award [1] for an answer:
a. accept either 35 / 34.8 / 34.78 (this answer may be expressed as negative) OR 53 / 53.3 / 53.33;
Do not award the mark if more than two decimal places shown or if the answer is incorrectly rounded up or down.

Award [1] for working, accepting any of the following:

OR other credible alternatives for working;

lack of FoxO1 (correlates) with low/decreased insulin and high/increased glucagon levels.

a. insulin used to take up/reduce glucose levels (after eating/when blood glucose levels high);
b. decrease in insulin in FoxO1 lacking/IKO mice would cause increase in glucose levels (as less is removed);
c. glucagon (used to convert stored carbohydrate to glucose) to increase glucose levels;
d. increase in glucagon (as seen in second graph, where IKO level higher than control) would mean more glucose added to blood/increase in glucose levels (on first graph);
e. (on first graph) see older/stressed/adult female mice with much higher glucose levels than young mice;

Most candidates achieved one mark. This was an unusual compare question as the similarity was that the data showed only slight differences and the differences were actually not significant. The correct answers less often given included the added notation that there was no significant difference, the observation that the data were clustered around a mean value of 0.8 mg ml–1 and the observation that there is nearly the same spread of data (least often noted).

Most candidates achieved this mark.

Many candidates got one or the other of the marks; better students got both by stating their answers as a formal deduction. The formality was not required for the mark, but seems to have been achieved by those who did

Many saw the relationship between older control and IKO mice but failed to comment on the relationship between younger control and IKO mice.

There are 2, possibly more, correct answers, depending upon the emphasis of the finding being discussed. So, the mark scheme limited acceptable answers to two possible numeric answers because, of the candidates who responded correctly, about half responded with 53% and the other half responded with 35%. There at least 5 ways to work through this problem correctly so the marking point for the working, was very generous. Partial working counted: all the way from extracting the correct data from the graphs (minimum) to display of all steps to an answer. All of these variations received marks for working. Numbers from the graph such as 2.3 and 1.5 were seen often but poor working. The mark was given anyway because necessary numbers were read from the graph. Working with percentages is an expectation given in the Mathematical Expectations in the course guide. Many candidates work with percentage change and percentage difference in their practical work. This is seen in the IA samples where schools are providing complex activities in the practical scheme of work.

As mentioned on the G-2 forms, this was an unusual format for asking candidates to detect correlations. However, where the answers really grappled with the idea of correlation, they usually performed well. They had to recognize that there are actually two correlations expected in the answer.
Wrong answers often described a causal relationship. Candidates did not seem to understand that when writing about correlation, causation should not be implied. A verb such as increases or decreases implies cause. However, the adjectives decreased insulin and increased glucagon are acceptable because the adjectives describe the conditions of the correlation. As such, the question assessed an authentic understanding of Topic 1 AS 1.1.6.

This question expected an application of information learned in Topic 6 (AS 6.5.11) to the data given. The command term is suggest which opens the door to reasonable analysis. Of the candidates who understood what was being asked, most earned two marks. They could gain one mark by recalling the function of insulin on blood glucose levels and another mark by recalling the function of glucagon. There were three additional marking points for interpreting the data as it would affect blood glucose levels because of the mutation. There were some excellent responses to this question, however, there were some really poor answers too. Candidates described when insulin and glucagon were released but not what the hormones would do. Many regarded insulin as an enzyme that breaks down sugar. Some students stated that glucagon was broken down into glucose. Some attempted to insert diabetes into the answer while others added the concept of stress.