Birthe Eriksen

Report of a European collaborative exercise comparing DNA typing results using a single locus VNTR probe

A collaborative exercise was carried out in 1989 among 12 European forensic laboratories using the single locus VNTR probe pYNH24, the restriction enzyme HinfI, the same set of human genomic DNA samples, and a standardized DNA size marker. The objectives of the exercise were: (1) to study the degree of variation within and between laboratories, (2) to obtain information on requirements for technical standardization allowing the exchange of typing results and (3) to compare different approaches for the identification of allelic DNA fragments of unknown size. Each laboratory carried out up to 10 independent typing experiments using the same DNA samples. The results were analysed independently by two laboratories using three different methods. The results of the exercise demonstrate the correlation of typing that can be achieved within and between laboratories under conditions of minimal standardization.

A report of an international collaborative experiment to demonstrate the uniformity obtainable using DNA profiling techniques

This paper describes a collaborative exercise intended to demonstrate whether uniformity of DNA profile results could be achieved between different European laboratories. It was shown that this goal can be obtained provided that a common protocol is followed (specifically the use of a common electrophoretic buffer as being the most important parameter). Generally, lower molecular weight loci (with lower molecular weight fragments) such as YNH24 perform better than higher molecular weight loci such as MS43a. The results of the exercise are discussed in relation to the objectives of the European DNA profiling group (EDNAP).

Results of a collaborative study regarding the standardization of the Y-linked STR system DYS385 by the European DNA Profiling (EDNAP) group

Y-chromosome linked short tandem repeat (STR) loci are inherited as a closely linked haplotype, which appears to remain stable in a given paternal lineage over many generations. In forensic cases, Y-linked STRs are particularly useful for the identification of human remains as well as in rape cases with mixed male/female stain samples. DYS385 is derived from tandemly duplicated segments of the Y chromosome thus giving rise to two fragments of variable length which do not behave like alleles but genotypes. The European DNA Profiling (EDNAP) group has carried out a collaborative exercise among 14 participating laboratories using DYS385 for typing of five unknown bloodstains and a control sample. Furthermore, population data from eight different European countries with samples sizes between 91 and 150 male individuals were collected. The results confirm previous observations that DYS385 is one of the most informative Y-linked STR loci. It could also be demonstrated that reproducible results can be obtained independently from the electrophoretic separation and detection methods used. Thus DYS385 may serve as a useful complementation to the routinely used autosomal STR systems in special cases.

Routine use of ultraviolet light in medicolegal examinations to evaluate stains and skin trauma.

The use of ultraviolet light induced fluorescence as an aid in forensic medical examinations of rape victims was evaluated preliminarily in a retrospective, non-consecutive study. In a four-month period, 17 cases were referred by the police for examinations at the Institute of Forensic Pathology. Ultraviolet light illumination (UVI) was used in seven cases, and in six cases fluorescent skin areas were observed. The fluorescence was due to lesions in four cases and stainings with saliva and semen in other two cases. In at least two cases, skin trauma detected with UVI were unobserved in ordinary light. It is concluded that UVI should be a routine part of forensic medical examinations. It may assist the forensic medical examiner in finding skin trauma and in locating stains, thus enabling retrieval of material for serological analyses. UVI is simple to carry out, requiring only a small, portable ultraviolet light source.

Statistical analysis of the measurement errors in the determination of fragment length in DNA-RFLP analysis.

DNA from human whole blood samples was digested with the restriction enzyme HinfI and RFLP analysis performed using the single locus probes MS1, MS31, MS43a and YNH24. The intergel variation of 3291 duplicate measurements of fragment lengths in terms of basepairs was investigated. The difference between two measurements of the same fragment on different gels increased approximately exponentially with increasing fragment length. After transformation of the fragment length into a normalized migration distance it was found that the difference between two transformed measurements was normally distributed with a S.D. (0.70 mm) which was independent of the fragment length. The errors of band 1 and band 2 on the same lane were correlated (r2 = 0.8). It is useful in the calculation of frequencies and in retrieval procedures and also in the calculation of likelihood ratios to be able to use a S.D. which is independent of the fragment length.

Human red cell esterase D polymorphism in Denmark, its use in paternity cases and the description of a new phenotype

Red cell esterase D (EsD) phenotypes were determined in a Danish population sample of 3,116 unrelated adults by starch-gel electrophoresis. A new phenotype was discovered, which appeared to be determined by the EsD1 allele and a new allele EsDCph. The gene frequencies observed were EsD1 = 0.9007, EsD2 = 0.0992, EsDCph = 0.0001. Investigation of 1,111 mother-child pairs and 59 families with 157 offspring added further support to the genetic model of two common alleles at an autosomal locus. The applicability of the EsD polymorphism to paternity testing was investigated on 960 cases of disputed paternity. An estimate of the EsD null allele frequency (0.001) in European populations was made on the basis of observations made on 5,864 mother/child combinations and 762 matings with 1,882 offspring. The influence of this allele on the reliability of exclusions of paternity was determined.

Case reportReport on the third EDNAP collaborative STR exercise

This report describes an inter-laboratory exercise completed on behalf of the European DNA Profiling (EDNAP) group. The exercise is one in a series designed to identify STR loci which could be used for harmonisation between participating European forensic science laboratories. Participants were asked to identify the alleles present in five bloodstains at the STR loci HUMTHO1 and HUMVWFA31/A. Two of the stains were prepared from mixtures of two different blood samples. There were no special instructions and each laboratory was requested to use the methodology normally employed for crime case investigations. All participating laboratories achieved the same results for both loci. In addition, the laboratories were also requested to report the results obtained from any other loci which would normally be used in crime case investigations. A comparison of these results showed some inter-laboratory variation.

Human Red Cell Glyoxalase I Polymorphism in Denmark and Its Application to Paternity Cases

Phenotypes of glyoxalase I (GLO) were determined in 1220 unrelated adults from all parts of Denmark giving the gene frequencies GLO1 = 0.4311 and GLO2 = 0.5689. The segregation of phenotypes in 59 families and in 455 mother-child pairs was consistent with the assumed autosomal codominant inheritance. The results of an investigation of 379 parternity cases with respect to exclusions of non-fathers by means of the GLO system are reported, and the application of the GLO system to paternity cases is discussed.

Sequencing strategy of mitochondrial HV1 and HV2 DNA with length heteroplasmy.

We describe a method to obtain reliable mitochondrial DNA (mtDNA) sequences downstream of the homopolymeric stretches with length heteroplasmy in the sequencing direction. The method is based on the use of junction primers that bind to a part of the homopolymeric stretch and the first 2-4 bases downstream of the homopolymeric region. This junction primer method gave clear and unambiguous results using samples from 21 individuals with length heteroplasmy in the hypervariable regions HV1, HV2 or both. The method is of special value for forensic casework, because sequencing of both strands of an mtDNA region is preferable in order to reduce ambiguities in sequence determination.

GEDNAP IV and V. The 4th and 5th Stain Blind Trials Using DNA Technology

In the collaborative exercise GEDNAP IV one EDTA blood sample (2 ml) and 5 bloodstains (0.5 ml on cotton) were investigated and in GEDNAP V, a total of 8 bloodstains (0.5 m1 on cotton), including 2 mixed bloodstains. DNA typing was carried out using the RFLP systems YNH24/Hinf I and MS43a/Hinf I and the PCR systems HLA DQα, D1S80, ApoB and YNZ22. In both exercises approximately 20 laboratories obtained results using the RFLP systems. Of the PCR systems, DIS80 was the most commonly used (14 labs in GEDNAP IV; 18 labs in GEDNAP V). The interlaboratory standard deviation for YNH24 in both exercises was approx. 0.6%, for MS43a 0.7–2.2% (GEDNAP IV) and 0.4–1.4% (GEDNAP V), depending on the fragment size. The fragment size calculation performed in each laboratory yielded a standard deviation twice that obtained when the fragment size calculation was performed centrally (IfR, Münster). In GEDNAP III, a system-specific corridor was developed to define the limits of deviation; this was modified for the present study by combining the fragment size ranges of YNH24 and MS43a. In both studies a subgroup of laboratories was involved in preliminary exercises using three PCR VNTRs and the system HLA DQα. Owing to the substantial variation in experience of the participating laboratories with PCR typing the results obtained in these two studies do not fulfil the basic quality criteria of the GEDNAP studies.