DNAstatistics LECTURE dna qPCR LESSONS.ppt

DNA

1. Statistical weights of
single source DNA profiles
Forensic Bioinformatics
(www.bioforensics.com)
Dan E. Krane, Wright State University, Dayton, OH
Forensic DNA Profiling Video Series

2. DNA statistics
•Coincidental 13 locus DNA
profile matches are
exceedingly rare
•Several factors can make
statistics less impressive
–Mixtures
–Incomplete information
–Relatives

3. DNA profile

4. Comparing electropherograms
Evidence sample Suspect #1’s reference
EXCLUDE

5. Comparing electropherograms
Evidence sample Suspect #2’s reference
CANNOT EXCLUDE

6. What weight should be given to
DNA evidence?
Statistics do not lie.
But, you have to pay close attention to the
questions they are addressing.

7. What weight should be given to
DNA evidence?
Statistics do not lie.
But, you have to pay close attention to the
questions they are addressing.
RMP: The chance that a randomly chosen,
unrelated individual from a given
population would have the same DNA
profile observed in a sample.

8. Single source
samples
Formulae for RMP:
At a locus:
Heterozygotes:
Homozygotes:
Multiply across all
loci
p
2
Statistical estimates: the product rule
2pq2pq 2pq2pq
2pq 2pq2pq2pq
2pq 2pq
2pq 2pq
2pq
p
2
p
2
p
2
x x x x
xx x x
x x x x
x
x

9. 0.1454x0.1097x2
Statistical estimates: the product rule

10. 3.2% 6.0% 4.6% 1.2%
9.8% 9.5% 6.3% 2.2% 1.0%
2.9% 5.1% 29.9% 4.0%
1.1% 6.6%
X X X X
XXXXX
X X X X
X
Statistical estimates: the product rule
1 in 609,000,000,000,000,000,000
1 in 609 quintillion
= 0.0320.1454 0.1097 2x x

11. Two underlying assumptions of the
product rule:
•The events being evaluated are independent
–In this context, the events are the
observation of specific alleles
•The frequencies of the events are known
–In this context, at what frequency does
each allele occur?

12. Population genetics: testing for
independence
•Hardy-Weinberg equilibrium (HWE)
–A test of the independence of alleles
within a locus
•Linkage equilibrium
–A test of the independence of alleles
between loci

13. DNA profile

14. DNA statistics
•Coincidental 13 locus DNA
profile matches are exceedingly
rare
•Corrections can be made for
population substructure
•RMP statistics described in terms
of quintillions are common

15. Two underlying assumptions of the
product rule:
•The events being evaluated are independent
–In this context, the events are the
observation of specific alleles
•The frequencies of the events are known
–In this context, at what frequency does
each allele occur?

16. What weight should be given to
DNA evidence?
Statistics do not lie.
But, you have to pay close attention to the
questions they are addressing.
RMP: The chance that a randomly chosen,
unrelated individual from a given
population would have the same DNA
profile observed in a sample.

17. What is the relevant population?
1 in 609 quintillion

18. Popular vote in 2008 by county. McCain won red
counties, Obama won blue counties.
How would you determine the frequency of
Obama supporters in North Carolina?
Obama
N.C. 50.2%

19. Popular vote in 2008 by county. McCain won red
counties, Obama won blue counties.
How would you determine the frequency of
Obama supporters in North Carolina?
Obama
N.C. 50.2%
Region 59.6%

20. Popular vote in 2008 by county. McCain won red
counties, Obama won blue counties.
How would you determine the frequency of
Obama supporters in North Carolina?
Obama
N.C. 50.2%
Region 59.6%
U.S. 52.9%

21. Popular vote in 2008 by county. McCain won red
counties, Obama won blue counties.
How would you determine the frequency of
Obama supporters in North Carolina?
Obama
N.C. 50.2%
Region 59.6%
U.S. 52.9%
Utah? 35.5%
?

22. DNA statistics
•Coincidental 13 locus DNA
profile matches are
exceedingly rare
•Several factors can make
statistics less impressive
–Mixtures
–Incomplete information
–Relatives

23. Statistical weights of
single source DNA profiles
Forensic Bioinformatics
(www.bioforensics.com)
Dan E. Krane, Wright State University, Dayton, OH
Forensic DNA Profiling Video Series