Isabella Spinetti

Inferring relationships between pairs of individuals from locus heterozygosities

BackgroundThe traditional exact method for inferring relationships between individuals from genetic data is not easily applicable in all situations that may be encountered in several fields of applied genetics. This study describes an approach that gives affordable results and is easily applicable; it is based on the probabilities that two individuals share 0, 1 or both alleles at a locus identical by state.ResultsWe show that these probabilities (zi) depend on locus heterozygosity (H), and are scarcely affected by variation of the distribution of allele frequencies. This allows us to obtain empirical curves relating zis to H for a series of common relationships, so that the likelihood ratio of a pair of relationships between any two individuals, given their genotypes at a locus, is a function of a single parameter, H. Application to large samples of mother-child and full-sib pairs shows that the statistical power of this method to infer the correct relationship is not much lower than the exact method. Analysis of a large database of STR data proves that locus heterozygosity does not vary significantly among Caucasian populations, apart from special cases, so that the likelihood ratio of the more common relationships between pairs of individuals may be obtained by looking at tabulated zi values.ConclusionsA simple method is provided, which may be used by any scientist with the help of a calculator or a spreadsheet to compute the likelihood ratios of common alternative relationships between pairs of individuals.

In vivo uptake of haemolymph from a female sterile mutant into wild-type ovaries of Drosophila melanogaster

Abstract A procedure has been developed in Drosophila by which haemolymph from a female sterile mutant can be used as a vitellogenic probe. This consists of labelling haemolymph proteins metabolically in flies homozygous for the female sterile mutation fs(3)H23. Developing ovarian follicles are then exposed in vivo to labelled mutant haemolymph by transfusing it into wild-type females. The criteria whereby mutant haemolymph can be used reliably instead of purified vitellogenin are as follows: yolk polypeptides should be the major protein fractions labelled after in vivo exposure to mutant haemolymph and, labelling in the recipient ovary should be confined to the yolk spheres. In this study we show that both of these criteria are fulfilled when mutant haemolymph is collected 48 h after [ 3 H]leucine injection.

Development of a heptaplex PCR system to analyse X-chromosome STR loci from five Italian population samples. A collaborative study

Abstract A heptaplex PCR has been developed to amplify DXS6789, HUMARA, DXS10011, DXS7423, HPRTB, DXS6807 and DXS101 on Italian samples from Bologna, Modena, Padova, Ancona and Pisa. Statistical analyses were performed for all the loci.

Polymorphism of plasminogen in Tuscany (Italy)

SummaryThe distribution of PLG phenotypes in the population of Tuscany (Central Italy) has been investigated by means of isoelectric focusing followed by immunofixation of desialyzed sera. In a random sample of 383 unrelated healthy blood donors registered at the Hospital of Pisa, three common phenotypes, PLG A, A-B, and B, and two rare variants were found. The allele frequencies calculated in our study were: PLG*A = 0.6749, PLG*B = 0.3225, and PLG*rare = 0.0026. The theoretical exclusion rate in cases of disputed paternity is 17.42%ZusammenfassungDie Verteilung der Plasminogen-Phänotypen in der Bevölkerung der Toskana wird untersucht. Die Bestimmung erfolgt an Neuraminidasebehandelten Seren nach isoelektrischer Fokussierung im Agarose-Gel und anschließender Immunofixation. In einer zufälligen Bevölkerungsstichprobe von 383 unverwandten gesunden Blutspendern des Krankenhauses Pisa wurden die drei neueren-Phdnotypen PLG A, A-B and B gefunden sowie zwei seltene Varianten. Die berechneten Allelfrequenzen unserer Studie waren: PLG*A = 0,6749, PLG*B = 0,3225 and PLG* seltene Var. = 0,0026. Die theoretische Ausschließungschance im Vaterschaftsverfahren beträgt 17,42%.

Italian data of 23 STR loci amplified in a single multiplex reaction

D4S2364 72–84 Tetra (ATTC) 4 0.578 0.013 D20S1082 77–98 Tri (ATA) 8 0.660 0.075 D9S1122 96–116 Tetra (TAGA) 6 0.683 0.063 D6S474 110–126 Tetra (complex) 5 0.765 0.020 D3S4529 114–134 Tetra (ATCT) 6 0.768 0.036 D17S1301 121–137 Tetra (AGAT) 5 0.680 0.089 D2S1776 152–176 Tetra (AGAT) 7 0.762 0.028 D12ATA63 166–187 Tri (complex) 8 0.807 0.009 D1GATA113 165–189 Tetra (GATA) 7 0.589 0.002 D2S441 169–197 Tetra (TCTA) 9 0.781 0.011 D22S1045 206–227 Tri (ATT) 8 0.741 0.096 D18S853 216–234 Tri (ATA) 7 0.718 0.039 D17S974 224–248 Tetra (CTAT) 7 0.694 0.008 D10S1248 253–273 Tetra (GGAA) 6 0.773 0.016 D20S482 259–287 Tetra (AGAT) 7 0.723 0.004 D6S1017 260–288 Tetra (ATCC) 7 0.675 0.067 D10S1435 262–294 Tetra (TATC) 9 0.732 0.052 D4S2408 310–326 Tetra (ATCT) 5 0.762 0.002 D3S3053 307–327 Tetra (TATC) 6 0.731 0.015 D14S1434 321–341 Tetra (complex) 6 0.723 0.009 D1S1677 310–342 Tetra (TTCC) 9 0.733 0.100 D5S2500 328–372 Tetra (complex) 8 0.731 0.028 D11S4463 356–384 Tetra (TATC) 8 0.771 0.051 Dear Editor,

The use of genetic markers to estimate relationships between dogs in the course of criminal investigations

ObjectiveAttacks on humans by dogs in a pack, though uncommon, do happen, and result in severe, sometimes fatal, injuries. We describe the role that canine genetic markers played during the investigation of a fatal dog-pack attack involving a 50-year-old male truck driver in a parking lot in Tuscany (Italy). Using canine specific STR genetic markers, the local authorities, in the course of their investigations, reconstructed the genetic relationships between the dogs that caused the deadly aggression and other dogs belonging to the owner of the parking who, at the moment of the aggression, was located in another region of Italy.Results From a Bayesian clustering algorithm, the most likely number of clusters was two. The average relatedness among the dogs responsible for the aggression was higher than the average relatedness among the other dogs or between the two groups. Taken together, all these results indicate that the two groups of dogs are clearly distinct. Genetic relationships showed that the two groups of dogs were not related. It was therefore unlikely that the murderous dogs belonged to the owner of the parking lot who, on grounds of this and additional evidence, was eventually acquitted.

Study of the APO B Polymorphism in Tuscany (Italy)

The APO B VNTR locus is located next to the 3′ end of the apolipoprotein B gene and consists of a series of AT rich tandem repeats, each 14–16 bp long (for a review about the genetic relationship between the 3′-VNTR and diallelic apolipoprotein B gene polymorphism, see Renges et al, 1992; for a recent proposal of a molecular model, see Desmarais et al 1993). Its polymorphism was described by Boerwinkle et al (1989) and by Ludwig et al (1989) using the PCR technique. Since then, the APO B has become a genetic marker quite frequently used in forensic practice.

The number of STR markers necessary to resolve relationships in deficiency paternity cases

Abstract The inference about the biological relationship between pairs of individuals using genetic markers plays a central role in many areas of human genetics. We investigated the number of markers (M) that are necessary to assign a given proportion of pairs (50%, 60%, 70%, 80%, 90%, 95%, and 99%) to their correct relationship at three predefined probability levels (99%, 99.9%, and 99.99%) against several alternative hypotheses. The following relationships were considered: (1) full sibs (FS), (2) second degree (2D, including half-sibs, grandparent–grandchild and avuncular pairs), (3) first cousins (FC), (4) unrelated individuals (UR).

Localization of DNA on a dishcloth used as a strangulation tool allowed perpetrator identification within a family

A case report of a domestic murder is presented. The victim was strangled with a kitchen cloth; the suspect, victims ex-husband, who still frequented the house, admitted of having used that cloth, though to dry his hands only. The pattern of DNA amplified from the cloth, belonging to both victim and suspect, allowed suspects version to be rejected. D 2003 Published by Elsevier B.V.

A multicentric study of SE33 allele frequencies in the Italian population

Allele and genotype frequencies for STR SE33 were obtained for a sample of 419 Italians in view of application in personal identification and paternity. D 2003 Elsevier Science B.V. All rights reserved.