.Question 1. Before starting the lab work, define the terms below. If necessary, look these up in your biology textbook and print the definitions in the spaces below
undefine dallele
undefined trait
undefined gene
undefined dominant
undefined recessive
undefined homozygous
undefined heterozygous
undefined genotype
undefined phenotype
undefined genetics
undefinedAABB X aabb Pundefined . . . .undefined AaBb
F1undefined undefined undefined
Question 2. Verify that the genotype of the F1 (above) is correct by doing the following:undefined
On the diagram above, write the genotypes of the parental gametes in the space below each parent (P) .
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Verify that the gametes you have written combine to form the F1genotype in the diagram.
Notice that while the order of the alleles does not matter, we group alleles for the same trait together, with capital letters first. This makes it easier to recognize whether individuals have identical genotypes.
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What is the phenotype of the F1generation?
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Question 3. An individual of genotype AaBb would produce 4 types of gametes. Remember that each gamete gets one allele from each gene pair. What are the 4 kinds of gametes that could be produced
?undefined
a)undefined b)
undefined c)
undefined d)
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Question 4. Identify the phenotype associated with each of the following genotypes:undefined
AA _________________________ BB _________________________undefined
Aa _________________________ Bb _________________________undefinedaa _________________________ bb _________________________undefined undefined(7.) Complete the “offspring” column of Table 1 by writing the genotype derived by combining the two gametes in fertilization. To make similar genotypes easily identifiable, always group alleles for the same trait together, and write the letter for any dominant allele first. (e.g., Ab + ab = Aabb). undefined
Table 1undefinedDihybrid Cross Laboratory Model:
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OBSERVED Genotypes of Offspring from the Cross
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AaBb X AaBb
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Note: Combine the first and second gametes to obtain the genotype of each offspring. For each offspring, group the alleles with the same letter together5, placing the capital letters first
undefined undefined Breeding First Gamete* Second Gamete Genotype of Offspring 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. undefined(8.) Count the observed number of each offspring genotype in Table 1. Tabulate these observed numbers according to the genotype list in Table 2.undefined(9.) Determine the phenotype for each offspring genotype and fill in the phenotype column of Table 2. Use your answers to Question 4 (above) to help you identify the phenotypes .undefined Table 2undefined undefined Tabulation of Offspring OBSERVED from the Dihybrid Cross undefined undefined AaBb x AaBb undefined undefined Genotype Number Observed Phenotype AABB AABb AAbb AaBB AaBb Aabb aaBB aaBb aabb undefined(8.) Count the observed number of each offspring genotype in Table 1. Tabulate these observed numbers according to the genotype list in Table 2.undefined(9.) Determine the phenotype for each offspring genotype and fill in the phenotype column of Table 2. Use your answers to Question 4 (above) to help you identify the phenotypes. undefined(10). Using the numbers from Table 2, add up the total observed offspring of each of the six possible phenotypes. Record these values in the “observed” column of Table 3.undefined undefined
Table 3undefined Phenotype Number Observed by your Team (from Table 2) Class Average Observed Number Expected from Punnett Square (see Table 4) curly hair, brown eyes wavy hair, brown eyes, straight hair, brown eyes curly hair, blue eyes wavy hair, blue eyes straight t hair, blue eyes undefined Send your Table to Number Observed to Instructor Before Friday 11/6/20undefined(11.) The instructor will give you the class averages by Friday 11/6/20, copy the class averages for observed numbers into the proper column of Table 3.undefined(12.)
To determine the expected numbers for the offspring phenotypes, complete the Punnett Square below (Table 4):undefined undefined
Write the genotypes of the 4 parental gametes in the indicated areas for each parent. (Recall you identified these in Question 3.) The first one has been done for you.
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In each of the 16 boxes of the Punnett Square, combine the row and column gametes to give the genotype of the offspring. Remember to group alleles with the same letter together, with the capital letters (dominant alleles) first.
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Add up all of the members of each phenotype in the Punnett Square and write the totals in the “expected” column of Table 3.
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Table 4undefinedPunnett Square: Calculating undefined undefinedEXPECTED Offspring Frequencies from the Dihybrid Crossundefined undefined(Parent #1) AaBb x AaBb (Parent #2)undefinedNote: Combine the first and second gametes to obtain the genotype of each offspring. For each offspring, group the alleles with the same letter together, placing the capital letters first.undefined GAMETE Genotypes – Parent #2 GAMETE Genotypes – Parent #1 undefined
Question 5. Which were closer to your expected numbers for the offspring of the dihybrid cross: your team’s observed numbers or the class averages? Which observed numbers are more reliable predictors of population values?undefined undefined
Question 6. Determine the probability of getting any of the 4 different kinds of gametes possible from each dihybrid individual. For help, refer to the following:undefinedThe probability of any gamete genotype is a fraction:
undefinedprobability = undefinedList all the gamete genotypes for an AaBb individual and indicate their probabilities:
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Question 7. A married couple both happen to be doubly heterozygous (dihybrid) for eye color and hair form. They have only one child who has blue eyes and straight hair. Determine the probability of this couple producing a child with the aabb genotype. Follow these steps:undefined
Write the probability of an ab gamete from an AaBb parent:
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At the time of fertilization, the probability of specific gametes getting together is the product of the individual probabilities for each gamete (this is known as the multiplicative law). Therefore, we can calculate the aabb probability using the following equation:
undefined (offspring with aabb ) = P(ab sperm) P(ab egg ) = undefined
Examine your Punnett Square (Figure 4).
undefined How many total boxes are there? undefined How many of these are the aabb genotype? undefined What fraction of the offspring are expected to be aabb? undefined
Your probability calculation should agree with the Punnett Square proportion for the aabb genotype – does it?
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Question 8. Among the members of your class, is there a preponderance of numbers in any particular range of numbers, such as 1-32? Try to account for this undefined undefined
Question 9. It is likely that more than one person in your class have the same “number” on the hereditary wheel. Do these people look like they might be identical twins? Do you see a similarity between them which you do not see with other members of the class?undefined
Considering the vastness of the human genome, comment on your observations. undefined undefined undefined undefined
Question 10. Do you suppose there are other Mendelian characteristics which could be added to a heredity wheel? undefined
How many different phenotypes would there be if you added just one more trait to the wheel? Two more traits? undefined
Question 11. Describe how the variety of human phenotypes illustrates one of the fundamental biological requirement for evolution by natural selection. (Read about the requirements for natural selection in your textbook if necessary.)undefined undefined undefined undefined undefined undefined undefined
Questions 12, 13, and 14 will not be done in this class. undefined undefined undefined
Use the information in Figure 2 to help you evaluate your blood type. Indicate your test results below. undefined
Did the “blood agglutinate?” (indicate + or -)undefined Antiserum Mr. Smith Ms. Jones Mr. Green Ms. Brown anti-A anti-B anti-D (Rh) “blood” phenotype comments undefined undefined undefined
Questions and Practice Problems
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Question 15. Blood transfusions aim to give the patient a temporary supply of erythrocytes until his body can manufacture enough of its own. It is desirable that the donor and the recipient of the transfusion be of the same blood type. But it has been found that a person of blood type O can safely give blood (in limited quantity, a pint seems always to be safe) to persons of any other blood type. Thus, type O is sometimes called the universal donor.undefined
How might this be explained? (Hint: refer to Figure 2.)undefined undefined undefined undefined undefined
Question 16. What complications might arise if large quantities of blood from a donor of type O were introduced into a recipient of any blood type other than O? undefined
Question 17. If persons of type O are sometimes called universal donors because they can donate to all other types, what blood type might be called the universal recipient? Why? (Refer to Figure 2.)undefined
Question 18. Explain the fact that blood types A and B each have two genotypes. undefined
Question 19. What blood types might occur among the children of a marriage between a person of blood type AB and a person of blood type O? Fill in the Punnett Square: show the gamete genotypes of each parent, then determine the offspring blood types.undefined
What is the probability of the parents having a child with type A blood?
Question 17
If you are blood type O and your father is also blood type O, what type or types must your mother be? (Write your father’s gamete genotypes and your own genotype on the Punnett Square. Then identify what you know about your mother’s genotype.) undefined
Possible genotypes of mother:undefinedCould these same parents have a child with blood type AB?
Explain.undefinedQuestion 20. Can a person of blood type A who marries a person of blood type B have type O children? (Explain your answer and show your work.)undefinedQuestion 21. If a homozygous Rh+ man fathered children with a homozygous Rh- woman, what fraction of the offspring would be Rh+? (Show your work: remember to first determine the egg and sperm genotypes.)undefined
Question 22. If an Rh- woman gave birth to an Rh- child, what could you conclude about genotype of the father?undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined
Question 23. Hemophilia is a hereditary disease characterized by poor clotting of the blood. As a result, hemophiliacs bleed excessively when injured. A certain kind of hemophilia is sex-linked and recessive. Sex-linked means that the allele for hemophilia is found on the X chromosome. Although recessive, the hemophilia allele (Xh) will determine the phenotype of the individual unless the individual is a female with a normal allele (XH) on her second X chromosome. undefined
Problem: A “normal” woman whose father was a hemophiliac marries a normal man. What genotypes and phenotypes are expected in the children and in what proportions? (When you are working with sex-linked traits, it is a good idea to include both types of sex chromosomes in your Punnett Square.)undefined
Question 24. It has been observed that there are more hemophiliac children of one sex than the other born in the general population. Explain. undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined
Question 25. The frequencies of the various blood groups have historically been quite stable in well-defined populations, i.e., they tend to remain unchanged in time, and characteristic of each group. The following chart shows these frequencies among several populations. Refer to Table 5 for the Biology 120 Class Frequencies and complete Table 6 by calculating the percentages of each blood type in your class.undefinedTable 6. Comparison of Blood Group Frequenciesundefined Population Blood Group Frequencies O A B AB Rh+ Rh- Japanese 25% 39% 24% 12% 99% 1% Whites (USA) 45% 38% 12% 5% 85% 15% Blacks (USA) 47% 28% 20% 5% 93% 7% Aborigines (Australia) 34% 66% 0 0 Eskimos (Labrador) 49% 51% 0 0 Pueblo Indians (New Mexico) 88% 12% 0 0 98% 2% Biology 120 Class (frequencies) Biology 120 Class (percents) undefined undefined
Question 26. Is the frequency distribution for the Biology 120 class similar to any of the others? Comment on this.undefined undefined undefined undefined
Question 27. Imagine that one of your lab partners thinks that recessive phenotypes must be “weaker” than dominant phenotypes. As a result, the student concludes that there must always be fewer recessive genes in the population. The student cites as an example the fact that there are fewer blue-eyed people than brown eyed people. Explain how you would use the information in this lab exercise to set your partner straight.undefined undefined
Question 28. Suggest some factors which might act to bring about changes in the relative proportions of the various blood groups in a population. (Hint: consider reasons why the ethnic composition of an area might change.)undefined undefined
Question 29. What factors might act to keep the blood group frequencies in a population fairly constant over time?undefined
Question 30. A man whose blood group genotype is AO marries a woman with Type AB blood. Assume both parents are also heterozygous for the Rh factor. Construct a Punnett Square which shows the genotypes of all possible offspring. Then organize the data: list all possible phenotypes, and the probability of this couple having any one of those phenotypes.undefinedParent genotypes: X
undefined undefinedPunnett Square:
undefined GAMETES from- Parent # 2undefined undefined GAMETE from- Parent # 1 undefinedExpected offspring phenotypes and probabilities are:
Requirements: N/A
