Caracterización de doce nuevos alelos observados en una muestra costarricense en el marcador STR de uso forense D18S51
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2009
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El Departamento de Ciencias Forenses en Costa Rica estudió aproximadamente 10,000 transferencias alélicas de padre/hijo y 14,500 madre/hijo utilizando los sistemas PowerPlex®16 y/o AmpF/STR®Identifiler® para detectar desviaciones de los patrones mendelianos de herencia esperados. En ambos sistemas se incluye el marcador de pequeñas repeticiones en tándem (STR) D18S51, un STR altamente polimórfico con una escalera de alelos conocidos en el rango de 7-27 repeticiones y que se encuentra ampliamente incluido en las Bases de ADN en el mundo. Se observó un patrón que sugería la presencia de alelos nulos o silentes en el locus D18S51 en 25 transmisiones alélicas paternas y en 43 maternas, puesto que tanto el progenitor como el hijo aparentaban ser homocigotos para diferentes alelos en el mismo locus Las exclusiones con perfiles homocigotas en D18S51 fueron previamente asociadas con patrones trialélicos en el locus Penta E cuando eran detectados por PowerPlex®16. Los presuntos alelos nulos fueron reanalizados con el uso de un juego de imprimadores alternos. Los 68 casos mostraron perfiles heterocigotos donde uno de los alelos de cada muestra se presentaba fuera del rango de la escalera alélica del D18S51. El análisis de las secuencias de los alelos fuera del rango de la escalera reveló doce nuevos alelos que se designaron de acuerdo con el número de repeticiones AGAA de la siguiente forma: 28, 29, 30, 31, 32, 33 , 34, 35, 36, 37, 38 y 40. Adicionalmente se presentan dos investigaciones de paternidad en las que se observó mutaciones de un paso en D 18S51 que involucraban los alelos 28 -29 y 31-32. Los alelos fuera del rango de las escaleras alélicas tienen serias implicaciones para el análisis semiautomatizado de los STRs porque pueden ser causantes de falsa pérdida de heterocigosis y falsos patrones de tres alelos. Por esta razón, nuestra observación debe ser considerada en la evaluación...
Inglés: Costa Rican Forensic Science Department studied approximately 10,000 father/child and 14,500 mother/child allelic transfers using PowerPlex®I6 and/or AmpF/STR®Identifiler® kits to detect deviations from expected Mendelian inheritance patterns. Both kits include the short tandem repeat (STR) marker D18S51, a very polymorphic STR. It has a high number of known alleles ranging from 7-27 and it is widely included in DNA databases. Suggestive patterns of silent or null alleles in the D 18S5 l locus were found in 25 paternal and 43 maternal allelic transmissions as parent and child appeared to be homozygous for different alleles at this locus. Homozygous exclusions in D18S51 were previously associated with a three-allele pattern in the Penta E locus when detected by PowerPlex®l 6. Presumptive null alleles were re-analyzed by using alternative primer sets. The 68 cases showed heterozygous profiles where one allele of each sample was out of the allelic ladder range. Sequence analysis of these off-ladder fragments revealed twelve novel alleles designated according to the number of AGAA repetitions as follows: 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 and 40. Additionally, two paternity cases showing single step mutations at D18S51 are presented, where alleles 28 -29 and 31-32 are involved. Off-ladder alleles have serious implications for the semi-automated STR analysis; it may cause false loss of heterozigosity and false three allelic patterns. For this reason, our observation should be considered in the evaluation of forensic profiles and DNA databases.
Inglés: Costa Rican Forensic Science Department studied approximately 10,000 father/child and 14,500 mother/child allelic transfers using PowerPlex®I6 and/or AmpF/STR®Identifiler® kits to detect deviations from expected Mendelian inheritance patterns. Both kits include the short tandem repeat (STR) marker D18S51, a very polymorphic STR. It has a high number of known alleles ranging from 7-27 and it is widely included in DNA databases. Suggestive patterns of silent or null alleles in the D 18S5 l locus were found in 25 paternal and 43 maternal allelic transmissions as parent and child appeared to be homozygous for different alleles at this locus. Homozygous exclusions in D18S51 were previously associated with a three-allele pattern in the Penta E locus when detected by PowerPlex®l 6. Presumptive null alleles were re-analyzed by using alternative primer sets. The 68 cases showed heterozygous profiles where one allele of each sample was out of the allelic ladder range. Sequence analysis of these off-ladder fragments revealed twelve novel alleles designated according to the number of AGAA repetitions as follows: 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 and 40. Additionally, two paternity cases showing single step mutations at D18S51 are presented, where alleles 28 -29 and 31-32 are involved. Off-ladder alleles have serious implications for the semi-automated STR analysis; it may cause false loss of heterozigosity and false three allelic patterns. For this reason, our observation should be considered in the evaluation of forensic profiles and DNA databases.
Descripción
Tesis (magister scientiae en microbiología)--Universidad de Costa Rica. Sistema de Estudios de Posgrado, 2009.
Palabras clave
ADN - ANALISIS, GENETICA FORENSE, GENETICA HUMANA, MARCADORES GENETICOS, POLIMORFISMOS GENETICOS