Distribuição de taxas de recombinação ao longo do cromossomo 4 de Arabidopsis thaliana e sua associação com elementos genômicos
Carregando...
Data
2010-03-29
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Goiás
Resumo
Recombination is one of the most important factors in the evolution of genome
organization. It provides the links between homologous chromosomes that ensure their
proper segregation during the first meiotic division. It is responsible for the creation of
novel allele combinations and yields genetic diversity on which evolutionary selection can
act. Double-strand DNA breaks (DSB) initiate meiotic recombination and when the 3
terminus of one of the broken strands invades the unbroken DNA molecule and primes
DNA synthesis a double Holliday junction must be resolved through some alternative
pathways. When homologous chromosomes exchange genetic material with each other, an
event of recombination or a crossover takes place, which may be seen through chiasma.
Citological, genetics, and molecular studies in many organisms have demonstrated that
crossovers have a non homogeneous distribution across chromosomes, and rather
concentrated in relative small DNA fragments usually called recombination hotspots. In
searching for genomic features associated with recombination hotspots a model fitted to
human genome data explained 42% of recombination rate variation in a 5 mega base pairs
scale. Despite the fact that genomes of some plant species have been already sequenced, up
to this moment, no research has been published concerning a high resolution
characterization of recombination rate variation across a plant s genome. This study used
OH- radical cleavage intensity estimates and sequence data of chromosome 4 of A. thaliana
and population genetic data from a public set of 250 thousand SNP genotypes obtained for
362 A. thaliana accessions to: i) characterize the recombination rate and linkage
disequilibrium (LD) distributions across the chromosome 4 in different scales; ii) search
for recombination hotspots; iii) evaluate probable associations between sequence motifs
and genomic features with recombination hotspots. The results have shown that the
distribution of recombination events across chromosome 4 of A. thaliana is very
concentrated: 50% to 60% of all recombination events spans in only 13% to 20% of the
total length of the chromosome. Genomic features as G+C percent (G+C%) and OHradical
cleavage intensity showed important associations with LD estimates in several
scales. The mean OH- radical cleavage intensity and G+C% showed redundancy in
correlation analysis with LD and recombination rates. Artificial strong and statistically
significant correlations arose from the usage of sliding windows. DNA fragments
considered as hotspots lay preferentially in the middle third of the chromosome, while
those characterized for having long range LD decay are most localized in the two distal
thirds of the chromosome.
Descrição
Palavras-chave
Citação
MARTINS, Adilson Santos. Distribution of recombination rates across the chromosome 4 of Arabidopsis thaliana and its association with genomic features. 2010. 141 f. Tese (Doutorado em Ciências Agrárias) - Universidade Federal de Goiás, Goiânia, 2010.