1. A "constitutive" process is one that is always present or active, whereas an "inducible" process is one that requires some stimulus or event to trigger its activity. In your journal, name and briefly explain two constitutive parts or processes that protect vertebrates from elements of their external environment.

2. Injected foreign substances ("antigens") induce molecules that bind (stick to) the antigen.

One can separate ("fractionate") molecules by column chromatography: Very small beads are placed in a tube. The beads have tiny pores, so smaller molecules can enter the pores but bigger ones can't. The beads in the tube are immersed in buffer, which fills the pores and the spaces between the beads. If a solution containing different sized molecules passes over this "column", bigger molecules have less volume to pass through than smaller ones before reaching the bottom, so big ones get to the bottom faster. You can make a standard curve showing how long (in terms of how much buffer passes through - known as the" elution volume") it takes for molecules of known size to get from top to bottom. You can then run unknowns and get an idea of their size based on their elution volume. Suppose you made such a column, passed four molecules of known size over it, and recorded their elution volumes in the following data table:
Molecular weight of standard (Kd) Elution Volume (ml)
1500 10
1000 50
500 100
100 150

Now assume you injected a rabbit with antigen, then took serum samples after both 7 and 21 days. You passed each sample over the column and recorded the elution volume for the induced antigen-binding molecules:
7 days after injection 25
21 days after injection 130

? Based on these data, what conclusions can you draw about these induced, antigen-binding molecules?

3.List the immune system's four basic properties; tell in one sentence what each means.

4. Background information: a) Mike and Jamie have two daughters, Robin and Polly; b) Antibodies are large proteins called immunoglobulins, abbreviated "Igs"; c) You are constantly bombarded with offending foreign agents, so everyone has antibodies in their serum all the time; d) When you immunize and then prepare serum from the blood of the immunized individual, the preparation is called an antiserum. Further, you usually indicate what it is directed against by specifying what (or who) you immunized, followed by what the antigen was. For example, we made a "rabbit anti-DNP-BSA" in last week's chalkboard experiment .
Experiment: You purified Igs from Jamie's serum and immunized Mike with them. You purified Igs from Mike's serum and immunized Jamie with them. After two weeks, you drew their blood and prepared sera, so you now have two antisera:: Jamie anti-Mike's Ig and Mike anti-Jamie's Ig. You mixed each antiserum with fresh serum samples from all four family members. The table below shows your data. A "+" indicates a precipitate, a "-" indicates none.

ANTISERUM Jamie Mike Robin Polly
Jamie anti-Mike's Ig - + + +
Mike anti -Jamie's Ig + - + +

? From these data, what conclusion(s) can be drawn about the genes that encode antibodies and their pattern of inheritance?

? BRIEFLY explain your reasoning.

5. List the surface marker phenotype (in terms of CD or other acceptable nomenclature) of each functional subset of lymphocytes found in secondary lymphoid organs.

6. A researcher assessed CD3+ cells from lymph nodes and thymus for the percentage expressing each possible combination of CD4 and CD8. The results are shown in the table below.
Organ Neither
CD4 nor CD8 Just CD4 Just CD8 Both
CD4 and CD8
LN 0% 70% 30 0
Thymus 5 30 20 45
Next she performed a similar assessment of CD3+ cells in the thymi of fetal mice at various days of gestation:
Days of
Gestation Neither
CD4 nor CD8 Just CD4 Just CD8 Both
CD4 and CD8
15 50% 0 0 50
18 20 10 0 70
21 10 20 15 55
? What do you conclude from the first table?

? Based on the second table, advance a hypothesis about the developmental relationships of the subsets defined by these markers?

? BRIEFLY describe one additional experiment you could do to further test your hypothesis.

See attached file for full problem description.

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