The cruciform DNA generated from alternating Pu–Py sequences is presumed to be a transient intermediate in genetic recombination. A cruciform by itself is not as stable as a linear duplex due to the energetically unfavorable single-stranded loop, and most likely exists as a minor species in equilibrium with duplex structures under “normal” or unstressed conditions. Under certain conditions, such as high negative supercoiling ( 85), low ionic strength, and the presence of Mg 2+, palindromic or alternating Pu-Py sequences can fold back on themselves to form two opposed hairpins, called a cruciform (cross-like) structure. The inverted repeat sequences in mRNA also play an important role as critical sites of interaction with various protein factors that are involved in the initiation of translation, termination of transcription, and hence in the regulation of gene expression. Palindromic sequences are the usual recognition sites for restriction enzymes and frequently occur as essential elements in regulatory regions. CruciformĬertain DNA sequences have a twofold inverted symmetry and are called self-complementary or palindromic sequences. Hyone-Myong Eun, in Enzymology Primer for Recombinant DNA Technology, 1996 a. When GNPs are modified using rabies virus glycoprotein (RVG) peptide, a targeting moiety to neuroblastoma, RVG-GNPs effectively accumulated at the tumor site ( Lee et al., 2016). Encapsulated calcium carbonate using poly( d, l-lactide- co-glycolide) and gas-generating polymer nanoparticles (GNPs) released carbon dioxide bubbles under acidic conditions and enhanced ultrasound signals. However, the success is dependent on an efficient delivery system to the target site within the host cell and nanodelivery systems are showing promising results ( Aravalli and Steer, 2016).ĭevelopment of safe and efficient theranostic gas-generating nanoparticles for targeted ultrasound imaging and treatment of neuroblastoma have been reported by Lee et al. Also Human PCSK9 gene in chimeric liver-humanized mice bearing human hepatocytes greatly reduced blood levels of human PCSK9 protein with minimal off-target mutagenesis ( Wang et al., 2016). As compared to zinc finger nucleases (ZFN) and transcription activator-like effector nucleases (TALEN), CRISPR/Cas9 is much simpler with higher specificity and less toxicity ( Li and Cao, 2015).ĬRISPR-CAS genome-editing system has been used recently to rectify liver-related genes under in vitro conditions in cell cultures. These cr-RNAs anneal to trans-activating cr-RNA (tracr-RNA) and direct sequence-specific cleavage in which a double-strand break (DSB) is created by Cas proteins. In the type II CRISPR/Cas9 system, short segments of foreign DNA termed “spacers” get integrated within the CRISPR genomic loci, transcribed, and processed into short CRISPR RNA (cr-RNA). Three types of CRISPR/Cas systems have been reported: types I, II, and III. CRISPR spacers recognize and cut these exogenous genetic elements via RNA-guided DNA cleavage in a manner analogous to RNA interference in eukaryotic organisms ( Marraffini and Sontheimer, 2008). The role of palindromic sequences called clustered regulatory interspaced short palindromic repeats (CRISPR) found in bacteria and archaea genome is basically to provide immunity against foreign genetic elements such as plasmids ( Barrangou et al., 2007) and phages ( Marraffini and Sontheimer, 2008). Jyotdeep Kaur, in Progress and Challenges in Precision Medicine, 2017 6.2 CRISPR-CAS Technology for Gene Editing and Precision Medicine These possible multi-allelic patterns need to be kept in mind so that a mixture is not expected when encountering multiple alleles at a single locus that could legitimately come from a single-source sample. Triplicated DYS385 alleles have also been reported ( Kayser et al. For example, one study found nine duplications for DYS19 in 7772 individuals ( Kayser et al. Sequence regions flanking STR regions may also be duplicated elsewhere in the Y-chromosome and may create artifacts when PCR primers are moved during multiplex assay design ( Butler & Schoske 2004).ĭuplications or triplications of several Y-STRs have been reported for DYS19, DYS390, and DYS391. ChrY duplications, which occur in single-source samples, can confuse or complicate mixture interpretation if scientists are not aware of this phenomenon ( Butler et al. These multi-allelic patterns may be inherited or passed on across generations as has been observed when studying father-son sample pairs ( Decker et al. Butler, in Advanced Topics in Forensic DNA Typing: Methodology, 2012 ChrY Locus Duplications or Triplicationsĭue to the palindromic sequences often found on ChrY, Y-STR loci can sometimes exhibit as duplications or even triplications.
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