Sampling Of Individuals For Dna Database

If possible, population databases for use in forensic DNA testing should contain unrelated individuals of known ethnicity. However, this may not be completely possible in a practical sense, as many laboratories are required to use samples

Table 20.3 Illustration of how minimum allele frequency values change with increasing the number of individuals sampled.

Number of Individuals (N)

Chromosomes Sampled (2N)

Minimum Allele Frequency (5/2N)

100

200

0.025

200

400

0.0125

500

1000

0.005

1000

2000

20 000

0.00025

10 000

20 000

0.00025

Table 20.4 (facing) Comparison of D13S317 allele frequencies between different population studies. Data sets are grouped according to ethnic/racial classification which categories are often defined by self-declaration when samples are collected. Alleles in bold are below the recommended minimum allele frequency of 5/2N (NRCII, 1996). Minimum and maximum values for each allele are listed under each section.

that have been made anonymous prior to study. In addition, categories of ethnicity or race are often subjective and may be based on perceived phenotype or cultural classification. Sampled individuals may have more than one easily definable racial background and may prefer to be grouped differently from a cultural standpoint than they might otherwise biologically. Finally, people who have been adopted or conceived through in vitro fertilization may not know their true genetic heritage.

While relatedness may not always be completely prevented, inclusion of some relatives in the database will not invalidate allele frequency estimates. Systematic bias in allele frequency estimates should only occur with inclusion of relatives if particular alleles substantially affect fertility or viability of offspring. However, markers used in human identity testing applications are selected to avoid this type of sampling bias. The primary purpose in trying to obtain unrelated individuals is to improve the precision of allele frequency estimates by increasing the number of independent genes sampled (i.e., to observe more alleles that would represent the population being studied).

Individuals included in a DNA database should be selected without prior knowledge of genotypes at the loci under examination to insure randomness of the samples. A frequent practice is to collect samples from blood donors or hospital volunteers. For example, the samples used to generate the STR typing data in Appendix II are from anonymous blood donors with self-identified ethnicities purchased from two different blood banks (Butler et al. 2003). Well-characterized population samples with anthropological descriptions would be desirable in many cases to carefully define population groups but are not necessary to obtain valid information in forensic DNA population databases. Self-declaration of ethnicity can be a suitable method of categorizing samples on the basis of ethnicity (see Walsh et al. 2003).

Broad racial/ethnic categories are usually adequate for most forensic databases, unless an isolated population is of interest, such as Native American Apache Indians. An examination of allele frequencies observed with different sample sets from around the United States demonstrates that the differences between sample sets within a racial/ethnic group are small (Table 20.4). Note for example, the D13S317 allele frequencies for African-Americans seen with Holt et al. (2002) versus the data from Appendix II (Butler et al. 2003). The most common allele in both data sets is allele 12, which has a frequency of 0.424 in Appendix II and 0.444 in Holt et al. (2002). Likewise, allele frequencies for Florida and Virginia Caucasians are very similar with the most common allele

Reference

Population (number typed)

D13S317 Allele Frequencies

African American

< 8

8

9

10

11

12

13

14

15

Appendix II

NIST U.S. Samples (n

= 258)

-

0.033

0.033

0.023

0.306

0.424

0.145

0.035

-

Holt et al. 2000

ABI U.S. Samples (n =

: 195)

-

0.036

0.023

0.023

0.272

0.444

0.141

0.062

-

Budowle et al. 2001

FBI U.S. Samples (n =

179)

-

0.036

0.028

0.050

0.237

0.483

0.126

0.036

0.003

Budowle et al. 2001

California (n = 200)

-

0.045

0.033

0.023

0.270

0.405

0.153

0.073

-

Budowle et al. 2001

Alabama (n = 124)

-

0.032

0.012

0.008

0.367

0.379

0.169

0.032

-

Budowle et al. 2001

Florida (n = 100)

-

0.015

0.030

0.010

0.310

0.380

0.180

0.075

-

Budowle et al. 2001

Virginia (n = 199)

-

0.030

0.025

0.013

0.329

0.405

0.148

0.048

0.003

Budowle et al. 2001

New York (n = 150)

-

0.017

0.040

0.003

0.340

0.420

0.143

0.037

-

Budowle et al. 2001

Illinois (n = 155)

0.003

0.016

0.042

0.013

0.326

0.361

0.171

0.068

-

Budowle et al. 2001

Minnesota (n = 150) Minimum value Maximum value

-

0.047 0.015 0.047

0.033 0.012 0.042

0.030 0.003 0.050

0.270 0.237 0.367

0.410 0.361 0.483

0.157 0.126 0.180

0.053 0.032 0.075

-

Caucasian

< 8

8

9

10

11

12

13

14

15

Appendix II

NIST U.S. Samples (n

= 302)

-

0.113

0.075

0.051

0.339

0.248

0.124

0.048

0.002

Holt et al. 2000

ABI U.S. Samples (n =

200)

0.003

0.115

0.078

0.068

0.313

0.283

0.098

0.043

0.003

Budowle et al. 2001

FBI U.S. Samples (n =

196)

-

0.100

0.077

0.051

0.319

0.309

0.110

0.036

-

Budowle et al. 2001

California (n = 150)

0.003

0.130

0.057

0.073

0.313

0.277

0.100

0.040

0.007

Budowle et al. 2001

Alabama (n = 150)

-

0.117

0.080

0.067

0.320

0.267

0.110

0.037

0.003

Budowle et al. 2001

Florida (n = 246)

0.002

0.120

0.087

0.059

0.323

0.254

0.124

0.031

-

Budowle et al. 2001

Virginia (n = 197)

0.003

0.137

0.064

0.048

0.317

0.277

0.114

0.038

0.003

Budowle et al. 2001

New York (n = 141)

-

0.121

0.082

0.053

0.348

0.277

0.085

0.036

-

Budowle et al. 2001

Minnesota (n = 150)

-

0.130

0.070

0.063

0.297

0.307

0.090

0.043

-

Budowle et al. 2001

Canada (n = 166) Minimum value Maximum value

-

0.093 0.093 0.137

0.093 0.057 0.093

0.045 0.045 0.073

0.301 0.297 0.348

0.301 0.248 0.309

0.124 0.085 0.124

0.042 0.031 0.048

-

Reference

Population

D13S317 Allele Frequencies

(number typed)

Hispanic

< 8

8

9

10

11

12

13

14

15

Appendix II

NIST U.S. Samples (n

= 140)

-

0.121

0

.154

0.100

0.236

0.221

0.118

0.046

0.004

Budowle et al.

2001

FBI U.S. Samples (n =

203)

-

0.067

0

219

0.101

0.202

0.217

0.138

0.057

-

Budowle et al.

2001

California (n = 200)

-

0.073

0

217

0.100

0.203

0.235

0.130

0.043

-

Budowle et al.

2001

Florida (n = 240)

-

0.115

0

115

0.077

0.306

0.229

0.108

0.050

-

Budowle et al.

2001

New York (n = 152)

-

0.092

0

112

0.066

0.240

0.306

0.141

0.043

-

Budowle et al.

2001

Michigan (n = 150)

0.003

0.143

0

.120

0.083

0.227

0.250

0.120

0.050

0.003

Budowle et al.

2001

Minnesota (n = 149)

-

0.121

0

195

0.064

0.262

0.228

0.084

0.047

-

Budowle et al.

2001

Arizona (n = 234)

-

0.109

0

135

0.098

0.235

0.239

0.126

0.056

0.002

Budowle et al.

2001

Mexico (n = 143) Minimum value Maximum value

-

0.091 0.067 0.143

0 0 0

231 112 231

0.070 0.064 0.101

0.196 0.196 0.306

0.252 0.217 0.306

0.122 0.084 0.141

0.039 0.039 0.057

-

Table 20.4 being allele 11 at 0.323 and 0.317, respectively. Therefore, estimates of DNA

(Continued) profile frequencies will likely not vary significantly if a Caucasian population data set from Florida was used versus data from Virginia.

Table 20.4 being allele 11 at 0.323 and 0.317, respectively. Therefore, estimates of DNA

(Continued) profile frequencies will likely not vary significantly if a Caucasian population data set from Florida was used versus data from Virginia.

Was this article helpful?

0 0
Get Pregnant - Cure Infertility Naturally

Get Pregnant - Cure Infertility Naturally

Far too many people struggle to fall pregnant and conceive a child naturally. This book looks at the reasons for infertility and how using a natural, holistic approach can greatly improve your chances of conceiving a child of your own without surgery and without drugs!

Get My Free Ebook


Post a comment