American Commercial Phenotypic Pattern and Homologous Chromosomes Questions please help with this document, please finish today. Let me know if you have any questions Genetics discussion
Worksheet 5
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1. A wild-type trihybrid soybean plant is crossed to a pure-breeding soybean plant with the
recessive phenotypes pale leaf (l), oval seed (r), and short height (t). The results of the threepoint test cross are shown below. Traits that are not listed are wild-type.
Phenotype
Number
Pale
648
Pale oval
64
Pale short
10
Pale oval short
102
Oval
6
Oval short
618
Short
84
Wild-type
98
1630
a. What are the alleles on each homologous chromosome of the parental wild-type trihybrid
soybean plant? Place the genes in the correct gene order. Use L, R, and T to represent dominant
alleles, and l, r, and t for recessive alleles. (10 pts.)
b. Calculate the recombination fraction between the adjacent genes. (10 points)
c. Calculate the interference value for these data. (5 points)
d. Use a goodness of fit test to determine if the pale and short phenotypes are independently
assorting. (10 points)
4. Curt Stern’s famous “Twin Spot” experiment showed that crossing over can occur during
mitosis. The flies that were studied were a dihybrid at two linked loci, the singed bristle sn and
yellow body y. The homologous chromosomes are as follows:
Describe the phenotypic pattern you would expect on the body of the fly if there was a mitotic
crossing over between a.) sn and the centromere, b.) sn and y, and c.) y and the telomere. Be
sure to explain how the patterns occur. (15 points)
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