Name: Key Class: Date: Understandng the Genetcs of Blood Groups Objectves: understand the genetcs of blood types determne the ABO blood type of unknown smulated blood samples predct, usng punnett squares, all the possble ways blood type alleles can combne durng fertlzaton. Prepare and examne a smulated blood smear under the mcroscope estmate the number of smulated blood cells n a gven area. Background: Blood s a tssue comprsed of four components: Plasma, red and whte blood cells, and platelets. Plasma s a clear, straw-colored lqud porton that makes up 55% of the blood. It s composed of a mxture of water, sugar, fat, proten and varous salts. In addton, plasma contans a number of blood-clottng chemcals that help to stop bleedng. Blood functons prncpally as a vehcle whch transports gases, metabolc waste products and hormones throughout the body. Surface protens on red blood cells determne an ndvdual's blood type. These surface protens are called antgens. The system used to classfy human blood s called the ABO System. Dr. Karl Landstener, an Austran physcan, receved the Nobel Prze n physology for ths dscovery n 1930. Wth the ABO system, the knds of antgens present on red blood cells determne the blood type. An ndvdual wth A antgens has Blood type A, one wth B antgens has Blood Type B, one wth both A and B antgens has Blood Type AB, and one wth no antgens on the surface of hs/her red blood cells has Blood Type O. As a result of these dfferent antbodes dfferent people can donate to only certan blood types and can only receve from dfferent blood types. (See Table 1) Notce that f you have blood type O you are consdered a unversal donor. Blood type AB s a unversal receptor. Table 1: Blood Types Summary Blood type Antgen on Red Blood Cells Antbodes n Plasma Can receve blood from... A A B O,A A,AB B B A O,B B,AB AB A and B None O,AB,A,B AB Can donate blood to... O None A and B O `O,A,B,AB Blood plasma has crculatng protens called antbodes. For example, ndvduals wth A surface antgen have ant-b antbodes; those wth B surface antgen have ant-a antbodes. Those wth both A and B surface antgens have no antbodes. Indvduals wth no surface antgens have both ant-a and ant-b antbodes. Blood typng s performed usng antserum-blood that contans specfc antbodes. Ant-A Serum, whch contans ant-a antbodes, and Ant-B Serum, whch contans ant-b antbodes, are used n ABO blood typng. To perform a blood typng test, ant-a and ant-b sera are each separately mxed wth a drop of sample blood and observed for agglutnaton, or clumpng. (See Table 2) Table 2: Agglutnaton Reactons n the ABO System ABO Agglutnaton Reacton Ant- A Serum Ant-B Serum Blood Type Agglutnaton No Agglutnaton A No Agglutnaton Agglutnaton B Agglutnaton Agglutnaton AB No Agglutnaton No Agglutnaton O
In addton to the A and B antgens, another mportant antgen on the surface of red blood cells s the Rh proten, named for the rhesus monkey n whch t was frst studed. People who have ths proten are 'Rh-postve, and those who do not are consdered Rh-negatve. Table 3: Frequency of ABO Blood types and Rh Factor n the U.S. Blood Type Frequency Percentage Blood Type & Rh Factor A 42 A+ 37 B A- 8 10 B+ 8 B- 2 AB 4 AB+ 3 AB- 1 O 44 O+ 35 O- 9 Frequency Percentage Genotype or I B I B or I B I B Phenotype (Blood Type) Type A Type B Type AB Type O The presence of antgens on the red blood cells s determned by co-domnant alleles. An allele s one of several dfferent forms of a gene that s present as a specfc locaton on a specfc chromosome. Human blood type s ndependent on three dfferent alleles, known as, I B and. The and I B are co-domnant, whereas the allele s recessve. Each of us has two ABO blood type alleles. We nhert one allele from our bologcal mother and another from our bologcal father. The par of alleles n our DNA that codes for a partcular blood type s called the genotype, whle the characterstcs of the trat that an ndvdual dsplays s referred to as the phenotype. Snce there are three dfferent alleles, there are sx dfferent genotypes for blood types, as shown n Table 4. Bologsts us a dagram called a Punnet Square to predct all the possble ways alleles can combne durng fertlzaton. The parents' genotypes are placed on the outsde of the square. Letters nsde show the possble allele combnatons for an offsprng. For example, f both parents' genotypes are, then the Punnett square wll show that there s 100% chance that all of the offsprng wll have the alleles, and nhert type A blood. However, t s also possble to have blood type A f you nhert an allele (A antgen) from one parent and an allele (no antgen) from the other. Remember that the allele s domnant and the allele s recessve. In the followng Punnett square, whlle all of the offsprng wll have blood type A there s a 50% chance that they wll nhert the or the genotype. However, f both parents have blood type A but have I a genotypes, then there s a 25% chance that one of ther offsprng wll have type O blood ( genotype) as shown n the Punnett square below. Smlarly, f you nhert an I B allele from each parent, or an I B allele from one parent and an allele from the other, you wll have Blood Type B. Offsprng wll have Blood Type AB, f they nhert an allele from one parent and an I B allele from the other. The followng Punnett Square shows the possble offsprng genotype combnatons resultng from two parents wth and I B genotypes. Under ths scenaro, there s a 50 % chance that offsprng wll have Blood Type A and a 50% chance that they wll have blood type AB.
I B I B I B I B I B I B I B I B I B However f both parents have Blood Type AB ( genotypes), then there s a 25% chance that the offsprng wll have Blood Type A, and a 50% chance that they wll have Blood Type AB, and a 25% chance that they wll have Blood Type B. Purpose: Under certan crcumstances, blood typng can be used to rule out a potental father, but t s not an exact method that can be used to establsh a parental lnk. Based on the typng results of the smulated blood samples provded and your knowledge of the nhertance of human blood groups, you wll determne whch of the two alleged fathers could possbly be excluded as the bologcal father. Materals: Ant-A Serum (smulated) Ant-B Serum (smulated) 4 blood samples (smulated) o o Chld o Alleged 1 o Alleged 2 1 blood typng tray Paper towels 1 set strrng stcks (Blue and Yellow) Procedure: 1) Place 5 drops of the mother smulated blood sample n the A and B wells on your blood typng tray. 2) Place 3 drops of Ant-A Smulated Serum n Well A. 3) Place 3 drops of Ant-B Smulated Serum n Well B. 4) Use a separate strrng stck to mx the smulated blood and serum n each well for about 10 seconds. 5) Carefully examne each well to determne f the smulated blood n each well has clumped or agglutnated. Record your results and observatons n Data Table 1. 6) Thoroughly rnse the tray and strrng stcks and repeat steps 1-6 to type the remanng, smulated blood samples- Chld, Alleged 1, and Alleged 2. Data: Smulated Blood Sample Agglutnaton n Well A (+/-) Agglutnaton n Well B (+/-) Blood Type (Phenotype) Genotypes Observatons + - A or Answers wll vary Chld - - O Answers wll vary Alleged 1 - + B I B I B or I B Answers wll vary Alleged 2 + + AB I B Answers wll vary
Data Analyss: Clumpng ndcates that the smulated blood sample contans antgens that reacted aganst the antbodes n the typng serum that you mxed t wth. If the blood n Well A s the only blood that agglutnates, or clumps, then the blood sample you tested s Type A blood. IF the blood n Well B s the only blood that agglutnates or clumps, then the blood sample you tested s type B blood. If the blood n both Well A and Well B agglutnate or clumps, then the blood sample you tested s type AB blood. If the blood n both Well A and Well B does not agglutnate or clump, then the blood sample you tested s Type O blood. 1. Based upon your blood typng results, could ether of the alleged fathers possbly be the bologcal father of the chld? Alleged 1 s blood type s B, whle the mother s blood type s A. Based upon ths Alleged 1 could possbly be the bologcal father of the chld wth type O blood, provded hs genotype s I B. 2. Would you defntely exclude ether of the two alleged fathers as the bologcal father of the chld? Explan. Alleged 2 could defntely be excluded as the bologcal father, snce the chld s blood type O ( genotype) and must have receved an I allele from each parent. The genotype of an ndvdual wth blood type AB s I B and therefore, Alleged 2 could not have passed on an I allele to the chld. 3. In ths actvty, what are the possble blood types of the bologcal father? Genotypes? The possble blood types of the bologcal father are A, B or O. The genotypes of the possble blood types of the bologcal father would have to be, I B or. 4. Could a man wth Type A blood and a woman wth type AB blood produce a chld wth type O blood? Explan. No. A chld wth blood type O ( genotype) receves an I allele from each parent. The genotype of an ndvdual wth blood type AB s I B and therefore, a mother wth type AB blood could not pass on an allele to the chld. 5. What would a chld s blood type be f the mother s type O and the father s type A? Under ths scenaro, the mother s blood type genotype s, whereas the father s blood type genotype could be ether or. The possble blood type outcomes could be determned usng the Punnett squares as shown. _ All chldren would have blood type A There s a 50% chance that the chldren would have type O and 50% chance for type A
6. What would the bologcal father s blood type be f the chld s type s A and the mother s s O? The bologcal father s blood type would have to be A or AB 7. What would the father s blood type be f both the mother and the chld have blood type A The Bologcal father s blood type would have to be A, AB or O. 8. Use a Punnett Square to determne the possble blood types of the chldren f the bologcal mother s blood type s A (genotype or ) and the bologcal father s blood type s AB (genotype I B ) I B I B I B I B I B I B There s a 50% chance that the chldren wll be Blood type A and a 50% chance that the chldren would be Blood Type AB. There s a 50% chance that the chldren would have type A blood, a 25% chance they would have Type AB blood, and a 25% chance they would have type B blood.