ABO Blood Test to Determine Paternity Essay

The ABO blood test was used in this lab to test which of the three fathers is the blood father of Andrea. The blood test that is closely related to the blood type of Andrea is the respective blood father. Each blood sample was mixed with synthetic anti-A, anti-B, and anti-Rh to test for clotting or not. Father #3 and Andrea were the only subjects tested with Rh positive with all other subjects Rh negative, resulting in Father #3 as the blood father.

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Table 1: Possible Child Blood Types
Table 1: Possible Child Blood Types

The purpose of this lab is to determine which father is the blood father of the child. The mother, Andrea, and three other fathers were tested by their blood type and Rh factor to determine the blood father. The ABO blood test determines the blood type of subjects by the alleles IA, IB, and i. The blood alleles IA and IB are codominant over i, meaning both of the alleles are dominant over the recessive i.

The antigen with the Rh factor is determined by D as dominant or d as recessive, with the Rh positive factor as dominant and the Rh negative factor as recessive. In the ABO blood test, synthetic blood samples and synthetic serum of Anti-A, Anti-B, and Anti-Rh are mixed respectively into a blood typing slide. If agglutination occurs as the samples are mixed, then the subject’s blood type is the respective A, B, or Rh factor. The father with the most closely related alleles with Andrea is the blood father by testing June, the mother, Andrea, and all the fathers.


The container vials with synthetic blood samples each are respectively the mother, the child, Father #1, Father #2, and Father #3. Each of the respective blood samples are used once ever round in the experiment. One of the blood samples is dropped into the blood typing slide under three labels; A, B, and Rh. After applying the blood sample, a drop of synthetic serum blue (anti-A) is dropped into well A. Synthetic serum yellow (anti-B) is dropped into well B. Synthetic serum clear (anti-Rh) is dropped into well Rh. Using the respective colored toothpicks, each well is stirred and checked for agglutination (clotting). The blood typing slide is washed and re-used for the next blood sample.


Table 2: ABO Test results

In Table 2, only Andrea and Father #3 showed agglutination when anti-Rh was mixed with their blood sample. The June and Andrea both showed clotting with anti-B serum. The child showed agglutination in all of the following serums.

Table 3: Blood Group Determination Table

Table 3 resulted with Andrea’s blood type assumed as AB negative. Father #3 was the only one with a positive blood type. The Child has a Rh group of Dd containing the recessive allele d due to her mother’s Rh group being homozygous recessive dd. Father #3 had a Rh group of D_ followed with an uknown allele because no known factor can support an exact second allele.


Father #3 is the blood father of Andrea because in accordance to the lab results. Andrea was tested to have a blood type of AB positive and the mother as B negative. The only possible blood types of a blood father from the results are blood types AB positive or A positive. Only father #3 showed a matching blood type to the following possible blood types. The lab results supported the fact that father #3’s blood type was most closely related to Andrea’s blood type.


Q, R. (2010, January 5). Paternity testing using ABO blood types is impossible. Retrieved 2010, from Boston Paternity; The DNA Solution Blog: http://www.bostonpaternity.com/blog/paternity-testing-using-abo-blood-types-is-impossible/

Biology 240 Lab Handout, Lab 4: Multiple alleles and the ABO blood type

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