Plasmodium vivax Duffy Binding Protein (PvDBP) is essential for interacting with Duffy antigen receptor for chemokines (DARC) on the surface of red blood cells to allow invasion. Earlier whole genome sequence analyses provided evidence for the duplications of PvDBP . It is unclear whether PvDBP duplications play a role in recent increase of P . vivax in Sudan and in Duffy-negative individuals. In this study, the prevalence and type of PvDBP duplications, and its relationship to demographic and clinical features were investigated. A total of 200 malaria-suspected blood samples were collected from health facilities in Khartoum, River Nile, and Al-Obied. Among them, 145 were confirmed to be P . vivax , and 43 (29.7%) had more than one PvDBP copies with up to four copies being detected. Both the Malagasy and Cambodian types of PvDBP duplication were detected. No significant difference was observed between the two types of duplications between Duffy groups. Parasitemia was significantly higher in samples with the Malagasy-type than those without duplications. No significant difference was observed in PvDBP duplication prevalence and copy number among study sites. The functional significance of PvDBP duplications, especially those Malagasy-type that associated with higher parasitemia, merit further investigations.
Mosquitoes of the Anopheles gambiae complex, namely Anopheles arabiensis (Patton, 1905) and Anopheles gambiae (Giles, 1902) are the major vectors of human malaria in the African continent. This study was conducted mainly to investigate the molecular biologyof members of the An. gambiae complex in Sudan and Republic of Southern Sudan. The molecular investigation involved identification of members of the An. gambiae complex using polymerase chain reaction (PCR) techniques based on DNA specific nucleotide differences in the intergenic spacer region (IGS) of the ribosomal RNA gene claster (rRNA) and partial sequencing and analysis of IGS regions. Adult Anopheles mosquitoes were collected from four sites in Kassala State, Sudan and from one site in Western Bahr El Ghazal State, Republic of Southern Sudan. In addition, An. arabiensis specimens, obtained from Sennar town laboratory colony (Sudan) was used in the study. Collection of Anopheles mosquitoes was done by hand capture using sucking tube (aspirator) during the rainy seasons of 2008, 2009 and 2010. The molecular investigation predicts the existence of two species within the An. gambiae complex, namely An. arabiensis and An. gambiae . An. arabiensis was found as the predominant Anopheles mosquitoes in all the collection sites while An. gambiae was found sympatrically with An. arabiensis in Republic of Southern Sudan. The analysis of the IGS fragments revealed moderate level of genetic variations within and between the An. arabiensis populations. An. gambiae individuals showed high genetic similarity. The genetic analysis revealed little population differentiation ( F st=0.067) and high migration rate (Nm=3.51) which indicated high gene flow between An. arabiensis populations collected from Kassala State localities. The phylogenetic relationships between the different populations of An. arabiensis and An. gambiae were investigated. The IGS regions of rRNA gene have been shown to be powerful markers for species identification and studying the genetic structure of members of An. gambiae complex.
Very rapid rates of gene conversion were observed between duplicated a-amylase-coding sequences in Drosophila melanogaster. This gene conversion process was also seen in the related species Drosophila erecta. Specifically, there is virtual sequence identity between the coding regions of the two genes within each species, while the sequence divergence between species is close to that expected based on their phy- logenetic relationship. The flanking, noncoding regions are much more highly diverged and do not appear to be subject to gene conversion. Comparison of amylase sequences between the two species provides a clear demonstration that recurrent gene conversion does indeed lead to the concerted evolution of the gene pair.
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