Molecular Markers for Human Sex Determination in Forensic Genetics Analysis

Sex determination is indispensable in forensic anthropology, sexual disorder, and also as part of large-scale genetic population studies. The purpose of this investigation is to determine the human sex from whole blood using multiplex PCR analysis. Blood samples from 75 male and 70 female healthy volunteers were taken from Tikrit city, Iraq. Our study identified a reliable set of three primer locus, namely SRY, ALT1 (internal control) and amelogenin locus. The SRY primer on the Y chromosome showed a 254 bp of PCR product, with 100% accuracy for human male identification. Thus, the pair of SRY primers was considered a strong genetic marker for human sex identification. Amelogenin regions in the Y chromosome showed a true positive band (236 bp) with 100% accuracy on sex identification. Amelogenin regions in X chromosome also showed positive bands (330 bp) in female samples and positive band in male samples except for two samples showed a negative band (null bands). The most obvious finding from this study is that multiplex PCR of ALT1 and SRY is consider as a reliable genetic marker for human sex identification. The research has also shown that amelogenin is good genetic marker for human sex identification.

Tight DNA-protein complexes isolated from barley seedlings are rich in potential guanine quadruplex sequences

Background The concept of chromatin domains attached to the nuclear matrix is being revisited, with nucleus described as a set of topologically associating domains. The significance of the tightly bound to DNA proteins (TBP), a protein group that remains attached to DNA after its deproteinization should be also revisited, as the existence of these interactions is in good agreement with the concept of the topologically associating domain. The work aimed to characterize the DNA component of TBP isolated from barley seedlings. Methods The tight DNA-protein complexes from the first leaves, coleoptiles, and roots of barley seedlings were isolated by purification with chromatography on nitrocellulose or exhaustive digestion of DNA with DNase I. Cloning and transformation were performed using pMOSBBlue Blunt Ended Cloning Kit. Inserts were amplified by PCR, and sequencing was performed on the MegaBace 1000 Sequencing System. The BLAST search was performed using sequence databases at NCBI, CR-EST, and TREP and Ensembl Plants databases. Comparison to MAR/SAR sequences was performed using http://smartdb.bioinf.med.uni-goettingen.de/cgi-bin/SMARtDB/smar.cgi database. The prediction of G quadruplexes (GQ) was performed with the aid of R-studio library pqsfinder. CD spectra were recorded on a Chirascan CS/3D spectrometer. Results Although the barley genome is AT-rich (43% of GC pairs), most DNA fragments associated with TBP were GC-rich (up to 70% in some fractions). Both fractionation procedures yielded a high proportion of CT-motif sequences presented predominantly by the 16-bp CC(TCTCCC)2 TC fragment present in clones derived from the TBP-bound DNA and absent in free DNA. BLAST analysis revealed alignment with different barley repeats. Some clones, however, aligned with both nuclear and chloroplast structural genes. Alignments with MAR/SAR motifs were very few. The analysis produced by the pqsfinder program revealed numerous potential quadruplex-forming sites in the TBP-bound sequences. A set of oligonucleotides containing sites of possible GQs were designed and ordered. Three of them represented the minus strand of the CT-repeat. Two were derived from sequences of two clones of nitrocellulose retained fraction from leaves and contained GC-rich motifs different from the CT motif. Circular dichroism spectroscopy revealed profound changes in spectra when oligonucleotides were incubated with 100 mM KCl. There was either an increase of positive band in the area of 260 nm or the formation of a positive band at 290 nm. In the former case, changes are typical for parallel G-quadruplexes and, in the latter, 3 + 1 structures. Discussion The G-quadruplexes anchor proteins are probably involved in the maintenance of the topologically associated domain structure.

Structural specificity effects of trivalent polyamine analogues on the stabilization and conformational plasticity of triplex DNA

Natural polyamines, i.e. putrescine, spermidine and spermine, are excellent promoters of triplex DNA. Using melting temperature (Tm) measurements and CD spectroscopy, we found that structural alterations on spermidine backbone, including methylation, or acetylation at the N1-, N4- and/or N8-positions had a profound influence on the stability and conformation of poly(dA).2poly(dT) triplex. The conformation of the polynucleotide complex underwent sequential changes from B-DNA to triplex DNA as the concentration of spermidine increased from 0 to 50 µM in a buffer containing 10 mM sodium cacodylate and 1 mM EDTA (pH 7.2). At 60 µM spermidine, the CD spectrum of triplex DNA was comparable with that of Ψ-DNA, with a strong positive band centred around 260 nm. A negative band was also found at 295 nm. At higher concentrations of spermidine, however, the intensity of the positive band progressively decreased and the peak intensity was found at a 1:0.3 molar ratio of DNA phosphate:spermidine. Temperature-dependent CD analysis showed that the Ψ-DNA structure melted to single-stranded DNA at temperatures above the Tm determined from the absorbance versus temperature profile. Comparable effects were exerted on the conformation of triplex DNA by Co(NH3)63+, an inorganic trivalent cation. Substitution of the N4-hydrogen of spermidine by a cyclohexyl ring or the fusion of the N4-nitrogen in a cyclic ring system, as in piperidine, enhanced the ability of spermidine analogues to stabilize triplex and Ψ-DNA forms over a wider concentration range compared with spermidine. These data demonstrate a differential effect of trivalent cations in stabilizing triplex DNA and provoking unusual conformations such as Ψ-DNA. Synthetic homologues of spermidine that stabilize triplex DNA over a wider range of concentrations than that stabilized by spermidine itself might have potential therapeutic applications in the development of an anti-gene strategy against several diseases, including cancer and AIDS.