Lidia Vidal-Rioja

Molecular analysis of chromosomal polymorphism in the South American cricetid,Graomys griseoflavus

Graomys griseoflavus is a South American phyllotine rodent widespread in Argentina that shows a high frequency of Robertsonian fusions (RFs). DNA restriction withEcoRI produced a 250-bp repeated family (EG250) specific for the genus. Southern hybridization and sequencing analysis indicate that the EG250 family is heterogeneous, comprising at least two subfamilies.In situ hybridized EG250 probe showed a centromere location in almost all chromosomes. In all karyomorphs C-banding was negative, but restriction enzyme banding (re-banding) withAluI andMboI showed centromeric blocks in the autosomes that will generate Robertsonian fusions. Thus, we found three groups of chromosomes: (a) EG250 and Re-banding negative; (b) EG250 positive and Re-banding negative; and (c) EG250 and Re-banding positive. We consider that group (b) is more the result of chromatin condensation state than that of the frequency of recognition sites for the enzymes used. Restriction enzyme blocks would appear in regions with heterochromatic EG250 subfamilies, while lack of banding would be due to decondensed EG250 subfamilies becoming an easier target for chromosomal restriction. It is suggested that heterochromatic EG250 DNA provides a favourable molecular environment for Robertsonian fusion occurrence.

Geographic Structure in Gran Chaco Amerindians Based on Five X-Chromosome STRs

ABSTRACT We investigated the genetic differentiation of five X-chromosome STR markers among five native South American Amerindian populations inhabiting three different areas of the Gran Chaco: Mocoví, Chorote, Wichí, Lengua, and Ayoreo. The observed genetic structure showed correspondence with geographic distribution more clearly than previous information obtained from autosomal STRs for the same samples. On the other hand, X-chromosome STR data did not agree with linguistic affinities. These markers proved to be informative for the study of the native populations of the Gran Chaco region.

Loss of nucleolar organizer regions during chromosomal evolution in the South American cricetid Graomys griseoflavus

Graomys griseoflavus is a South American phyllotine rodent having a remarkable Robertsonian polymorphism which may have produced reproductive isolation between 2n=42−41 and 2n=38−34 karyomorphs. Analysis of nucleolar organizer region (NOR) locations both by silver staining (Ag-NOR) and in situ hybridization revealed that 2n=42 individuals exhibit highly variable Ag-NOR patterns, while specimens of the 2n=38−34 karyomorphic group showed a single Ag-NOR pattern. The latter animals underwent two NOR deletions in reference to the 2n=42 karyomorphs, one of which would be the consequence of a Robertsonian fusion and the other would be produced by the unequal crossing-over mechanism. The differential NOR homogenization supports the hypothesis that G. griseoflavus karyomorphs are evolving separately towards the acquisition of separate species status.

Análisis de diversidad genética en tres poblaciones de llamas (Lama glama) del noroeste argentino

Este trabajo describe la variabilidad genetica actual de tres poblaciones de llamas (Lama glama) del noroeste argentino (NOA), afectadas a la produccion de fibra. Originariamente, las tropas fueron una unica poblacion la cual fue subdividida hace 10 anos. Se estudiaron muestras de ADN de 77 animales mediante amplificacion por PCR de 12 loci microsatelite con cebadores especificos de llama. La alta variabilidad genetica comprobada se sustenta en el hallazgo total de 140 alelos diferentes, 9 a 16 alelos por locus y rangos de heterocigosidad observada y esperada por locus de 1 a 0 y 0,9 a 0,47, respectivamente. Diecinueve de treinta y seis pruebas de equilibrio de Hardy-Weinberg mostraron desvios significativos (P < 0,05) debidos a una deficiencia de heterocigotos que se corresponderia con el comportamiento poliginico natural de la especie. El nivel de diferenciacion genetica observado entre los tres planteles, moderado (Fst = 0,076; P = 0,000) pero significativo de subestructura, podria atribuirse a la introduccion de progenitores machos de otras regiones geograficas, en el momento de subdividir la poblacion original. La presencia de 44 alelos privados, distribuidos entre las tres tropas permitiria disenar apareamientos dirigidos a mejorar la diversidad genetica mediante el intercambio de nuevas variantes alelicas. La transferencia a los productores, de los resultados de este trabajo, beneficiara la adopcion de futuras estrategias de manejo adaptadas a la situacion particular de cada plantel

Heterochromatin and late replication in the chromosomes of the rat

The distribution of heterochromatin in the chromosomes of the rat was determined by analysing two of its properties: late replication and differential stain with the DNA d-r method. The presence of late and non-late replicating c-heterochromatin in the genome of Rattus norvegicus indicates that this chromatin is an heterogeneous substance exhibiting different properties. Furthermore, the existence of heterochromatin formed by nonrepeated sequences or by sequences with a low degree of repetitiveness is suggested by the presence of late replicating areas which do not react with the DNA d-r method.

South American camelid illegal traffic detection by means of molecular markers

South American camelids comprise the wild species guanaco and vicuña and their respective domestic relatives llama and alpaca. The aim of the present study was to determine by DNA analysis to which of these species belong a herd of camelids confiscated from a llama breeder but alleged to be alpacas by the prosecution, and to evaluate the usefulness of mitochondrial and autosomal DNA markers to solve judicial cases involving camelid taxa. Cytochrome b and cytochrome oxidase I mitochondrial genes and 7 STR were analyzed in 25 confiscated samples. Mitochondrial results were inconclusive because 18 of the sequestered samples presented haplotypes that corresponded to the guanaco haplogroup and the remaining seven belonged to a vicuña linage. Microsatellite data of casework samples and llama reference samples revealed different genetic profiles by the presence of private alleles at two microsatellites suggesting that the confiscated animals could be alpaca, or at least alpaca hybrids instead of pure llama.

The complete mitochondrial DNA sequence of the guanaco (Lama guanicoe): comparative analysis with the vicuña (Vicugna vicugna) genome

South American camelids comprise the guanaco (Lama guanicoe) and the vicuña (Vicugnavicugna), which are wild species, and the domestic llama (Lama glama) and alpaca (Lama pacos). This paper presents the first complete mitochondrial (mt) genome of the guanaco and the mt coding sequence of the vicuña. The guanaco mtDNA is 16,649 nt long and its composition and organization are similar to the mitochondrial genome of other mammals. Excluding the control region, comparison of the complete guanaco and vicuña mtDNA showed 4.4% sequence divergence. Nucleotide differences in peptide coding genes varied from 1.9% in ATP6 to 6.4% in Cyt b. These values are compatible with the close relatedness of both species identified by other authors. Based on the differences between the control region sequence here reported and that previously described, we also discuss the occurrence of NUMTs in the genome of South American camelids.