Biology 163 Laboratory in Genetics Midterm 2, Nov. 14, Honor Pledge: I have neither given nor received any unauthorized help on this exam:

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1 1 Biology 163 Laboratory in Genetics Midterm 2, Nov. 14, 2005 Honor Pledge: I have neither given nor received any unauthorized help on this exam: Name Printed: ignature: 1. Normally you need to cross two parents to get offspring. Name two model organisms we have discussed in class or used in the lab that can fertilize themselves to produce offspring. (2 pts) C. elegans Arabidopsis Maize a. Describe the phenotype of the unc mutant in C. elegans. (1pt) Paralyzed because of lack of muscles. Uncoordinated b. Is the unc32 mutant allele dominant or recessive? (1pt) recessive 3. You did a mutant screen to find corn plants that are resistant to a newly developed herbicide. From 4000 M2 plants, you selected 1 mutant that can grow on the herbicide. Normally the next step is to determine if your mutant is dominant to wild type or recessive. You use your mutant as female parent and fertilize it with wild type pollen. You also do the reverse cross, i.e. you fertilize the ears of a wild type plant with pollen from a mutant. You test the plants of the next generation for resistance to the herbicide to see if resistance is dominant or recessive to susceptibility. Here are the results of each cross:

2 2 Mutant X wildtype: 270/270 herbicide resistant. Wildtype X mutant: 250/250 herbicide sensitive. For the next generation cross, you take one of the 270 herbicide resistant plants that resulted from the Mutant X wildtype cross, and fertilize it with pollen from a wild type plant you get the following result: 200/200 herbicide resistant. Again you do the cross in both directions. You take the same herbicide resistant plant and use its pollen to fertilize a wild type plant. You get the following result: 200/200 herbicide sensitive. If you use the herbicide sensitive plant from the wildtype by mutant cross, all the progeny are sensitive to herbicide no mater which plant is used as male or female parent. Explain the inheritance of herbicide resistance. (2 pts) It is maternally inherited. 3. Explain the difference between maternal inheritance and maternal effect? (2 pts). Maternal inheritance is genetic transmission through cytoplasmic alleles Maternal effect is a trait that depends on the mother s genome, not the embryo. 5. Given the following results for scoring three Polymorphic markers (m1, m2, m3) in a mouse mapping array made analysis of backcross progeny after crossing strain B by strain and then backcrossing the heterozygous animals to line, which two markers are closest? (2 pts) numbers represent individual backcross mice: m1 B B B B B B B B B B B B B B m2 B B B B B B B B B B B B B B m3 B B B B B B B B B B B M1 and M3 are most alike and therefore more closely linked

3 3 6. How can you tell if a fruitfly is virgin or not and what does this mean about the age of the fly? I do not mean watch to see if she is laying eggs. (2 pts) Clear belly that allows you to see intestines inside. Mark of newly eclosed adult. Less than 8 hours old. 7. You think a DNA polymorphic marker A is linked to a disease. You have two small families with the disease to analyze. You calculate the following lod scores for each family. Family 1 LOD 0.8 Family 3 LOD 0.5 What is the LOD score for the combined family data? (1pt) 1.3 If you found a third family with a LOD score of -0.3, would the probability of linkage in this family be greater or less than 1? (1 pt) Less than 1. What would this third family do to your assumption that marker A is linked to the disease? (1 pt). Make it less likely. Make you think the marker may not be linked What would you do to further test if Marker A was linked to the disease? (1 pt) Collect more families and analyze their alleles for marker A. 8. The father of the family depicted below has a dominant trait for detached earlobes. His children illustrated with filled in boxes or circles have detached earlobes. You have investigated the inheritance of three DNA markers in this family. In each case, the mother is homozygous for her alleles at the marker in question, making it easier to follow the inheritance of the father s alleles. Which marker is closest to the gene for earlobe attachment. (1pt) M1 only one recombinant Which is furthest away? (1 pt)

4 4 M3 is unlinked M1 M2 M3 9. You are working with wild asters in the mountains of Virginia. You have found two plants in nature that both have white flowers. You bring them back to your home greenhouse. You collect self fertilized seed from each plant and you cross some flowers of each plant. You find that if you self fertilize either plant, all the progeny plants are white. You also cross each plant to a plant with purple flowers. All the F1 from this cross have purple flowers. When you cross the two white plants together, the F1 progeny from your crosses all have purple flowers. Are the alleles for white flowers recessive or dominant? (1 pts) Recessive Why do the F1 progeny from the two different white plants you collected in nature have purple flowers? (1 pt)

5 The mutations complement. The two original white flowered plants have mutations in two different genes. 5