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Human Genetics and Medicine - BIOL 72    Homework - Exam 2 supplement   Due 3/22

1.  A geneticist's preliminary results, and the results of a second, larger study are shown below.  In both cases, known doubly heterozygous organisms were test crossed.  Analyze each experiment separately, and then draw a conclusion about the MOST LIKELY map of the two genes tested, that is, are the genes assorting independently?  If the conclusions  differ, explain which you think is correct, and why you think it is more likely to be valid.

       Experiment A     Experiment B
HG         30                       300
Hg          21                       210
hg           26                       260
hG          23                       230

2.  How different from 50:50 is within acceptable tolerance for a process that is hypothesized to be random with 2 options (such as boy-girl; heads-tails, etc.)?  Using χ2 analysis, work out the “border” between acceptable and unacceptable results for a sample size of 10, 100, and 1000.  Convert these results into % values, and explain why they are different for the different sample sizes.

3.  Draw a pedigree for the following family: A man comes to you for advice because his aunt and his grandfather, both on his father’s side, and the son of his father’s sister, all have a weird birthmark behind their ear.  His wife knows that one of her uncles and one of her aunts also had it, but all she know of her mother’s family is that her mother 6 siblings.  Her father’s older brother had it, too, but not her father; there are only 2 children in that family.  The younger of her father’s 2 nephews and the elder of the 2 nieces also have it.  The man’s mother has 2 older sisters. Each has an older boy and a younger girl but none of them have the birthmark.  However, her younger brother has it and so does his only daughter.

What are the chances that the man and his wife will have a child with the birthmark?  Is it different for boys and girls?  Explain.

 


Table: Chi-Square Probabilities

df 0.995 0.99 0.975 0.95 0.90 0.10 0.05 0.025 0.01 0.005
1 --- --- 0.001 0.004 0.016 2.706 3.841 5.024 6.635 7.879
2 0.010 0.020 0.051 0.103 0.211 4.605 5.991 7.378 9.210 10.597
3 0.072 0.115 0.216 0.352 0.584 6.251 7.815 9.348 11.345 12.838
4 0.207 0.297 0.484 0.711 1.064 7.779 9.488 11.143 13.277 14.860
5 0.412 0.554 0.831 1.145 1.610 9.236 11.070 12.833 15.086 16.750
6 0.676 0.872 1.237 1.635 2.204 10.645 12.592 14.449 16.812 18.548



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