Answers are posted here.
1. You observe a 1:2:1 ratio of visible types in the F2 generation of a cross between two homozygous lines of corn. Choose the correct statement(s) about this result.
2. You cross two mouse strains heterozygous for four genes (AaBbCcDd). What proportion of the total offspring would be heterozygous for all four genes?
3. Choose the correct statements about tetrad analysis.
4. Choose the correct ordering of the events in meiosis.
Events:
5. Choose the correct statement(s) about the packing of DNA in a chromosome.
6. The ABO system in humans has three alleles. Choose the correct statements about this system.
7. Which of the following would represent "ideal" qualities of a research organism for genetic studies?
8. Choose the correct statement(s) about chromosome abnormalities in humans
9. Which are the correct statements about the Chi-square test used for testing "goodness of fit" in genetic crosses?
10. A woman with normal vision who is heterozygous for colorblindness (X-linked recessive) is also heterozygous for another gene on the X chromosome (D), 10 map units from the colorblindness gene, which can be detected using DNA tests. The 76 allele of the D gene and the allele causing colorlindness both came to her from her father. She also is carrying the 53 allele of the D gene.
Assuming that her husband has normal vision and carries the 86 allele of the D gene, what proportion of all of their children will be colorblind boys carrying the 53 allele of the D gene?
11. genotype-
12. testcross-
13. Hershey-Chase experiment-
14. allele-
15. telomere-
16. heterochromatin-
17. Klinefelter syndrome-
18. allopolyploid-
19. satellite DNA-
20. incomplete penetrance-
21. (10 points) The following cross is performed in fruit flies: +++/+++ X abc/abc to give F1 progeny of the genotypes +++/abc. These F1s are crossed with abc/abc testers, giving the following cross:
+++/abc X abc/abc
The following testcross progeny are observed:
Genotype |
Number |
+++/abc |
331 |
abc/abc |
313 |
++c/abc |
104 |
ab+/abc |
92 |
+bc/abc |
80 |
a++/abc |
76 |
+b+/abc |
3 |
a+c/abc |
1 |
Note: The table from #22 has been corrected. MSWord's automated capitalization feature messed up the genotypes
22. What is the map distance between the A, B and C genes in the cross below, and which are apparently located on the same chromosomes? The heterozyous parent arose from a cross of an AABBCC and an aabbcc individual. (10 points).
Parents AaBbCc X aabbcc
Progeny phenotypes |
Numbers of progeny |
ABC |
205 |
ABc |
205 |
abC |
195 |
abc |
195 |
AbC |
44 |
Abc |
57 |
aBC |
43 |
aBc |
56 |
23. The distance between genes based on recombination (genetic map distance) often does not correspond to the distance between genes based on the length of DNA between the genes on the chromosome. Explain why this is true. (5 points)
24. Given the following results from tests for a DNA marker (E) located at the centromere of chromosome 21 in the parents of a Down syndrome child and in the child herself, interpret which parent provided the extra chromosome and at which meiotic division the error occurred. (5 points).
Father has E 46 and E 63 alleles.
Mother has E 85 and E 32 alleles.
Down syndrome daughter has E 46, E 63 and E 32 alleles.
25. Briefly describe one DNA-based method for detecting polymorphisms that can be used for genetic mapping, paternity and criminal cases. (5 points)
26. White flower color is recessive to other flower colors in peas. Two strains of white-flower-colored pea plants are crossed and give purple-colored F1 hybrids. The F2 generation gives a 9:7 ratio of purple flowered to white flowered plants. Briefly explain this result. (5 points).