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Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen. While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.

These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens

on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur.

Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.

The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.

A couple decide to have a child. If the father's genotype is AO and the mother has type B blood of unknown genotype, which of the following are possible blood types for their child?

I. A

II. B

III. A, B

IV.

O

A.

I and II only

B.

I, II, and III only

C.

I, II, and IV only

D.

I, II, III, and IV

Where in a virus is the genetic material contained?

A. tail

B. capsid

C. sheath

D. plug

Which of the following is called DIOL?

A. Glycerol

B. Glycol

C. Methanol

D. Ethanol

When glucose is heated with Fehling's solution, the colour of the precipitate obtained is:

A. black.

B. yellow.

C. red.

D. white.

What is the identity of the reducing agent and oxidizing agent, respectively, in the reaction shown below?

2Cr(OH)3 + 3H2O2 + 4NaOH 2Na2CrO4 + 8H2O

A. Cr(OH)+ and NaOH

B. Cr(OH)3 and H2O2

C. H2O2 and Cr(OH)3

D. H2O2 and NaOH