Were the babies switched? The Genetics of Blood Types i

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Were the babes swtched? The Genetcs of Blood Types Two couples had babes on the same day n the same hosptal. Dense and Earnest had a grl, Tonja. Danelle and Mchael had twns, a boy, Mchael, Jr.

looked more lke twns snce they both had darker skn, whle Mchelle had lghter skn. Danelle nssted that both famles have blood type tests to check whether there had been a mx-up.

1 Were the babes swtched? The Genetcs of Blood Types Two couples had babes on the same day n the same hosptal. Dense and Earnest had a grl, Tonja. Danelle and Mchael had twns, a boy, Mchael, Jr., and a grl, Mchelle. Danelle was convnced that there had been a mx-up and she had the wrong baby grl. Tonja and Mchael Jr. looked more lke twns snce they both had darker skn, whle Mchelle had lghter skn. Danelle nssted that both famles have blood type tests to check whether there had been a mx-up. The Genetcs of Blood Types Each person has one of the blood types shown n ths chart. Your blood type s determned by whether your red blood cells have type A and/or type B carbohydrate molecules on the surface. A Person Wth: Has: Type A blood Type B blood Type A carbohydrate molecules Type B carbohydrate molecules Type AB blood Type O blood Both type A and type B carbohydrate molecules Nether type A nor type B carbohydrate molecules These four dfferent blood types result from dfferent alleles of a sngle gene n the DNA. These alleles gve the drectons for makng dfferent versons of a proten enzyme that puts dfferent types of carbohydrate molecules on the surface of red blood cells. Allele I A I B Gves the drectons for makng a verson of the enzyme that: puts type A carbohydrate molecules on the surface of red blood cells puts type B carbohydrate molecules on the surface of red blood cells s nactve; doesn't put ether type of carbohydrate molecule on the surface of red blood cells 1. Each person has two copes of ths gene, one nherted from hs/her mother and the other nherted from hs/her father. Complete the followng table to relate genotypes to blood types. Genotype Ths person's cells make: Blood Type I A I A the verson of the enzyme that puts type A carbohydrate molecules on the surface of red blood cells. the nactve proten that doesn t put ether type A or type B carbohydrate molecules on the surface of red blood cells. I A both the verson of the enzyme that puts type A carbohydrate molecules A on the surface of the nactve proten 2. In a person wth the I A genotype, whch allele s domnant, I A or? Explan your reasonng. 1

2 3. For the genotypes lsted below, whch type(s) of enzyme would ths person's cells make? What blood type would the person have? Genotype Wll ths person's cells make the verson of the enzyme that puts ths carbohydrate on the surface of hs/her red blood cells? I B I B Type A yes no; Type B yes no I B Type A yes no; Type B yes no Blood Type I A I B Type A yes no; Type B yes no AB Codomnance refers to nhertance n whch two alleles of a gene each have a dfferent observable effect on the phenotype of a heterozygous ndvdual. Thus, n codomnance, nether allele s recessve both alleles are domnant. 4. Whch of the genotypes lsted above results n a blood type that provdes clear evdence of codomnance? Explan your reasonng. Ths expanded verson of a Punnett square shows how meoss and fertlzaton result n the nhertance of genes. 5. Complete ths chart to show the genetc makeup of each zygote produced by fertlzaton. A baby develops from a zygote by repeated rounds of mtoss, so each cell n a baby s body has the same genetc makeup as the zygote. Ths s the genotype of the chld. 6a. Draw a Punnett square n the usual format for ths same mother and father. 6b. Wrte n the blood type for each parent and each chld. Notce that meoss and fertlzaton can produce: chldren who have the same blood type as one of ther parents chldren who have a dfferent blood type than ether parent. 2

Usng Immune Responses to Test Blood Types Our bodes can make antbodes aganst antgens such as the type A and type B carbohydrate molecules on the surface of red blood cells.

When an antbody bnds wth an antgen on the surface of a cell, ths can result n damage to the cell.

Do you thnk that a person wth type A blood makes ant-a antbodes or ant-b antbodes? Explan your reasonng. 8. Fll n the blanks n ths chart.

antbodes n your blood. If you have type AB blood, both type and type antgens on nether ant-a nor ant-b antbodes n your blood.

3 Usng Immune Responses to Test Blood Types Our bodes can make antbodes aganst antgens such as the type A and type B carbohydrate molecules on the surface of red blood cells. Each specfc type of antbody bnds to a specfc antgen. For example, ant-b antbodes n the blood bnd to type B antgens, but not to type A antgens. When an antbody bnds wth an antgen on the surface of a cell, ths can result n damage to the cell. Fortunately, your body generally does not make antbodes aganst any antgens that are part of your body. 7. Do you thnk that a person wth type A blood makes ant-a antbodes or ant-b antbodes? Explan your reasonng. 8. Fll n the blanks n ths chart. If you have type A blood, If you have type B blood, type A antgens on type B antgens on antbodes n your blood. antbodes n your blood. If you have type AB blood, both type and type antgens on nether ant-a nor ant-b antbodes n your blood. If you have type O blood, nether type of antgen on the surface of your red blood cells and both and antbodes n your blood. If you are gven a blood transfuson that does not match your blood type, antbodes n your blood can react wth the antgens on the donated cause them to burst and/or clump together and block blood vessels. Ths type of transfuson reacton can be fatal. To prevent ths from happenng, doctors test whether donated blood s compatble wth a person s blood before they gve a blood transfuson. 9. Explan how a type A blood transfuson could be fatal for a person wth type B blood. 3

4 10. If a blood sample has antgens that match the antbodes, ths wll result n clumpng. To test the blood type of each parent and each baby, you wll: mx one sample of hs/her blood wth ant-a antbodes to test whether hs/her blood has the type antgen mx a second sample of hs/her blood wth ant-b antbodes to test whether hs/her blood has the type antgen. 11. To prepare to nterpret the blood type tests, fll n the followng chart. Wll ths blood type clump f mxed wth Blood type ant-a antbody? ant-b antbody? A B AB O Procedure Your group wll need a blood-typng tray or other testng surface for each person lsted below. Go to the staton for each person and: Put three drops of the person s blood on the locaton to test for the type A antgen and put three drops on the locaton to test for the type B antgen. Put three drops of ant-a antbody soluton on the approprate blood sample and put three drops of ant-b antbody soluton on the other blood sample. Return to your seat and mx each blood sample and antbody soluton wth a clean toothpck. Dscard each toothpck after you have used t. If your testng surfaces are transparent, put them on a whte background so you can more easly see whether there s a clumpng reacton. For each person, record the results of both tests n the table below. Wrte n the blood type and possble genotypes of each person. Results Danelle (mother of twns) Mchael (father of twns) Dense (mother of daughter) Earnest (father of daughter) Mchael Jr. (boy twn) Baby grl 1 (grl twn, accordng to hosptal) Baby grl 2 (daughter of Dense and Earnest, accordng to hosptal) Reacts wth ant-a antbody (Yes or No) Reacts wth ant-b antbody (Yes or No) Blood type (A, B, AB, O) Possble genotype or genotypes 4

5 Interpretaton Now, you wll use the results of your blood tests to evaluate whether Danelle and Mchael s baby grl was swtched wth Dense and Earnest s baby grl. 12a. Draw Punnett squares for each possble combnaton of genotypes for Danelle and Mchael. Wrte n the blood type for each genotype to show the possble blood types for Danelle and Mchael s chldren. 12b. Draw Punnett squares for each possble combnaton of genotypes for Dense and Earnest. Wrte n the blood type for each genotype to show the possble blood types for Dense and Earnest s chldren. 12c. Who are the parents of each baby grl? How do you know? 12d. Were the babes swtched? By Drs. Jennfer Doherty and Ingrd Waldron, Dept Bology, Unv Pennsylvana, An alternatve verson of the Student Handout wth more genetcs and less mmunobology, together wth Teacher Preparaton Notes wth background nformaton and nstructonal suggestons, are avalable at 5

Were the babies switched? The Genetics of Blood Typesi

Were the babies switched? The Genetics of Blood Typesi Two couples had babies on the same day in the same hospital. Denise and Earnest had a girl, Tonja. Danielle and Michael had twins, a boy, Michael,