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CRISPR interference (CRISPRi) is a genetic perturbation technique that allows for sequence-specific repression of gene expression in prokaryotic and eukaryotic cells. [1] It was first developed by Stanley Qi and colleagues in the laboratories of Wendell Lim , Adam Arkin, Jonathan Weissman , and Jennifer Doudna . [ 2 ]
The basic model of CRISPR evolution is newly incorporated spacers driving phages to mutate their genomes to avoid the bacterial immune response, creating diversity in both the phage and host populations. To resist a phage infection, the sequence of the CRISPR spacer must correspond perfectly to the sequence of the target phage gene.
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
Human germline engineering (HGE) is the process by which the genome of an individual is modified in such a way that the change is heritable. This is achieved by altering the genes of the germ cells, which mature into eggs and sperm.
Professor of biology Jerry Coyne sums up biological evolution succinctly: [3]. Life on Earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.
Lentiviral delivery of designed shRNAs and the mechanism of RNA interference in mammalian cells. RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression.
CRISPR RNA or crRNA is a RNA transcript from the CRISPR locus. [1] CRISPR-Cas (clustered, regularly interspaced short palindromic repeats - CRISPR associated systems) is an adaptive immune system found in bacteria and archaea to protect against mobile genetic elements , like viruses , plasmids , and transposons . [ 2 ]
See: Guide RNA, CRISPR. Complementary base pairing between the sgRNA and genomic DNA allows targeting of Cas9 or dCas9. A small guide RNA (sgRNA), or gRNA is an RNA with around 20 nucleotides used to direct Cas9 or dCas9 to their targets. gRNAs contain two major regions of importance for CRISPR systems: the scaffold and spacer regions.