Biology Reference
In-Depth Information
Table 8.2
The profile frequency has been recalculated from Table 8.1 using the Balding
correction for sampling bias. The impact of this correction factor is greatest on the rare alleles
Locus
Alleles
Allele
Allele
Corrected allele
HWE
Genotype
frequency
count
frequency
proportion
D3S1358
15
0.2825
113
115/404
=
0.2847
2pq
0.1282
17
0.2225
89
91/404
=
0.2252
vWA
14
0.0850
34
36/404
=
0.0891
2pq
0.0450
17
0.2500
100
102/404
=
0.2525
D16S539
11
0.2975
119
121/404
=
0.2995
2pq
0.1068
13
0.1750
70
72/404
=
0.1782
D2S1338
24
0.1000
40
42/404
=
0.1040
2pq
0.0257
25
0.1200
48
50/404
=
0.1238
D8S1179
11
0.0625
25
27/404
=
0.0668
2pq
0.0466
13
0.3475
139
141/404
=
0.3490
D21S11
30
0.2625
105
107/404
=
0.2649
2pq
0.0577
31.2
0.1050
42
44/404
=
0.1089
D18S51
14
0.1675
67
69/404
=
0.1708
2pq
0.0499
15
0.1425
57
59/404
=
0.1460
D19S433
14
0.3275
131
133/404
=
0.3292
2pq
0.0196
15.2
0.0250
10
12/404
=
0.0297
THO1
9
0.1375
55
57/404
=
0.1411
2pq
0.0992
9.3
0.3500
140
142/404
=
0.3515
p
2
FGA
21
0.1775
71
75/404
=
0.1856
0.0345
21
0.1775
71
75/404
=
0.1856
Profile frequency
1.4225
×
10
−
13
populations of the same broad ethnic group, the population is not homogeneous but
comprises related subpopulations. The subpopulations form because people do not
mate randomly but tend, for example, to have children with people from the same
geographical area or same social group. Allelic databases are normally composed of
samples that have been drawn from the general population, and not from one subpop-
ulation, and therefore provide us with an average estimate of the allele frequencies
in the whole population. The effect of subpopulations has been demonstrated as
leading to errors in the estimation of profile frequencies [33]. In a subpopulation
there is a higher degree of relatedness between individuals than there is to the
whole population, that is a higher probability that two individuals would have some
genetic markers in common through descent from a common ancestor (identical by
descent) than by a random match (identical by state) [34]. To incorporate population
substructure factor, and thereby account for variations in allele frequencies between
different
subpopulations,
into
the
profile
frequency
calculations,
a
theta
value
(
) is used to describe the degree of differentiation between subpopulations (the
amount of inbreeding) [35, 36]. Actual levels of population substructure in human
populations have been demonstrated to be low [31, 32, 37, 38]. A theta value of
0.01 is commonly used for seemingly homogeneous populations, whereas for more
isolated/differentiated populations a theta value of 0.03 has been recommended
[31]. It seems better to have empirical estimates of theta and use those for specific
populations; however, that might not be practicable in all cases [39].
θ
