Genetics and Immunology

Question 1

The use of EDTA plasma prevents activation of the classical complement pathway by_____________.

a. causing rapid decay of complement components
b. chelating Mg ions which prevents the assembly of C6
c. chelating Ca ions which prevents assembly of C1
d. Enhancing the actions of C1 inhibitor

Answer 1

c. chelating Ca ions which prevents assembly of C1

The classical pathway is one of three activation pathways of the complement system, which is a major contributor to the defense of infections, clearance of pathogens, removal of apoptotic/nectrotic cells, and maintenance of hemeostasis.

The classical pathway is activated by an antigen-antibody reaction. The binding of C1q initiates teh sequential activation of the eleven proteins. The classical pathway has a clacium-dependent step (C1q, C1r, C1s).

EDTA anticoagulant chelates Calcium ions (Ca+) so that the classical complement cascade cannot initiate.

In the IRL serum (red top not containing EDTA) is sometimes preferred as complement dependent antibodies can be detectable!

Question 2

The expected frequency of an inherited gene combination is 35%. Population testing reveals that the observed frequency of the same gene combination is 55%. This is an example of:

a. Independent segregation
b. Hard-Weinberg Law
c. Crossing Over
d. Linkage Disequilibrium

Answer 2

d. Linkage Disequilibrium

Linkage Disequilibrium, which is when two genes are inherited togetehr more often that expected statistically

Question 3

In a given population, 16% of individuals are tested as Rh-. What is the gene frequency of the D antigen?

a. 0.4
b. 0.6
c. 0.16
d. 0.32

Answer 3

b. 0.6

We know that 15% of teh population is dd (D-). The square root of 0.16 is 0.4, which is the frequency of d gene. Remember that p+q = 1.0, or that the frequency of teh two genes is equal to 100% so, we know that q is 0.4 from above. Therefore, 1-q=p or 1-0.4=0.6

Frequency of D gene is 0.6 or 60%