US Population Samples

(Appendix II)

0.450 -,

0.400 -

0.350

o

0.300

n e

0.250

^

CT

0.200

e

LL

0.150 -

0.100 -

0.050

**

10 11 12 D13S317 Allele

□African-Americans (N=258) □ Caucasians (N=302) □ Hispanics (N = 140)

there is usually a decrease in heterozygotes and an increase in homozygotes. This population substructure can be adjusted for with the use of a correction factor referred to as 8 (NRC II, p. 102). The NRC II report recommends the use of 8 = 0.01 for general populations and 8 = 0.03 for small, isolated populations where inbreeding is more likely (see NRC II recommendations in Appendix VI). This correction factor is applied to genotype frequency estimates as described in Chapter 21 (e.g., Table 21.4). Data supports the NRC II recommendation that a value for Fst (8) of 0.01 is conservative for U.S. populations (Budowle and Chakraborty 2001, Budowle et al. 2001).

Sewall Wright defined the inbreeding coefficient, F, to compute any degree of relationship between parents (Wright 1951). The kinship coefficient is also designated by F and used to measure degree of relationship between two people (NRC II, p. 99). Fst is Wright's measure of population subdivision (Wright 1951) and is the same as theta (8) when mating within subpopulations is random. F-statistics can be thought of as a measure of the correlation of alleles within individuals and are related to inbreeding coefficients (NRC II, p. 102). F-statistics describe the amount of inbreeding-like effects within subpopulations (Fst or 8), among populations (Fis or f), and within the entire population (Fit or F). Weir and Cockerham (1984) and Weir and Hill (2002) contain more information on calculations behind 8 and the theory of population substructure.

PRACTICAL CONSIDERATIONS

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