Estimating The Most Common And Rarest Genotypes Possible

Another measure to reflect the usefulness of a particular set of DNA markers is to examine the frequencies of the most common genotypes, which would therefore be the least powerful in terms of being able to differentiate between two unrelated individuals (Edwards et al. 1992). The theoretically most common type can be calculated by considering a sample type that is heterozygous at all loci possessing the two most common alleles at each locus (Foreman and Evett 2001). For example, with D13S317 the two most common alleles in U.S. Caucasians are 11 (frequency of 0.33940) and 12 (frequency of 0.24834) (see Appendix II).

In Table 20.9 frequencies from the two most common alleles at each of the 13 CODIS loci are used to estimate a theoretical most common STR profile, which occurs with a frequency of approximately 6.26 X 10-12 or 1 in 160 billion. The rarest theoretical 13-locus profile, using the 5/2N minimum allele frequency

Locus

A1

A2

Allele 1 Freq (p)

Allele 2 Freq (q)

Genotype

Frequency

D13S317

11

12

0.33940

0.24834

2pq

0.1686

D16S539

12

11

0.32616

0.32119

2pq

0.2095

D18S51

15

16

0.15894

0.13907

2pq

0.0442

D21S11

30

29

0.27815

0.19536

2pq

0.1087

D3S1358

15

16

0.26159

0.25331

2pq

0.1325

D5S818

12

11

0.38411

0.36093

2pq

0.2773

D7S820

10

11

0.24338

0.20695

2pq

0.1007

D8S1179

13

12

0.30464

0.18543

2pq

0.1130

CSF1PO

12

11

0.36093

0.30132

2pq

0.2175

FGA

22

21

0.21854

0.18543

2pq

0.0810

TH01

9.3

6

0.36755

0.23179

2pq

0.1704

TPOX

8

11

0.53477

0.24338

2pq

0.2603

VWA

17

18

0.28146

0.20033

1.60 x 1011 (160 billion)

Table 20.9

Calculations for theoretically most common genotype frequencies and profile frequency based on two most common alleles found in a U.S. Caucasian allele frequency database (Appendix II).

Table 20.9

Calculations for theoretically most common genotype frequencies and profile frequency based on two most common alleles found in a U.S. Caucasian allele frequency database (Appendix II).

rule or 0.00828 in the case of the Caucasian database in Appendix II, and calculated with heterozygous rare alleles is as follows:

(2pq)13 = [2(0.00828)(0.00828)]13 = 6.06 x 10-51 (1.65 x 1050).

Thus, based on the allele frequencies present in a U.S. Caucasian database and independence assumptions between alleles and loci, the theoretical 13-locus STR profile estimates can range from 6.26x 10-12 to 6.06x 10-51.

Was this article helpful?

0 0
Stuttering Simple Techniques to Help Control Your Stutter

Stuttering Simple Techniques to Help Control Your Stutter

Discover Simple Techniques to Help Control Your Stutter. Stuttering is annoying and embarrassing. If you or a member of your family stutters, you already know the impact it can have on your everyday life. Stuttering interferes with communication, and can make social situations very difficult. It can even be harmful to your school or business life.

Get My Free Ebook


Post a comment