Page 12 - An Identity Crisis
P. 12
Post-Lab and Calculations
Solutions
Short Answer
1. Which woman was Louise Mondelo? 8. Given that there are only 8,300 people in the
The woman in the cabin. county where Highland Park is located, how
many people in that county would you expect
to find with the same genotype as each of the
2. Could the driver of the car be the mother of
the two children in the car? unknowns?
Yes. She shares one allele with each of the other 8,300 multiplied by each of the ‘combined
car crash victims. frequencies’ A: 1389, B: 257, C: 986, D: 720, E:
224, F: 1132
3. Of the known samples, who could have been
Jan’s parents? Wally’s? 9. Assuming an STR with 5 alleles (ignoring
Jan: Louise, Lyle, Woman in Car the very rare ‘off ladder’ alleles), how many
Wally: Louise, John Gretzky, Woman in Car genotypes exist?
Students may write all of them out, or use
the formula (n2+n)/2. There are 15 possible
4. Of the known samples, whose DNA could be genotypes.
on the firewood?
Louise, Jan, Woman in Car
10. Using the information from #9 above and
assuming that every STR has 5 alleles, on
5. Of the known samples, whose flesh could have average, how many STRs are needed to
been left on the fireplace? expect to find only one person of a given
None of the samples genotype in a population of 300 million?
Since there are 15 possible genotypes per
5-allele STR, the matching population is
6. Is it easier to prove that two DNA samples
match or do not match? reduced by 1/15 for every STR used. As such,
To prove conclusively that two samples match, we must determine how many times to multiply
all alleles must match. A single discrepancy, 1/15 by itself so that, when multiplied with the
however, will prove that the samples do not. population size of 300 million, we arrive at 1.
7. Is it easier to prove guilt or innocence using
DNA? With P= 300,000,000, x = 7.2
Answers will vary. Discuss the various
viewpoints and student reasoning
12 THE MYSTERY OF LYLE AND LOUISE
