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#specificity

6 public questions tagged with this topic.

Transgenic Plant -2

CRISPR/Cas9 specificity is provided by:

Specificity of CRISPR Cas9 system is dictated predominantly by guide RNA rather than protein itself, contrasting with zinc finger and TALEN protein-guided recognition. Cas9 from Streptococcus pyogenes contains recognition lobe and nuclease lobe with HNH and RuvC domains, plus PAM interacting domain at C-terminus that scans DNA for 5'-NGG-3' PAM via major groove interactions, required for binding. Spontaneous DNA unwinding initiates RNA-DNA heteroduplex formation with 20 nt spacer of crRNA embedded in single guide RNA fusion with tracrRNA scaffold. Complementarity drives conformational activati

Ref: Jinek et al. Science 2012 337:816 Cas9 guide RNA; Nishimasu Cell 2014 156:935 specificity.

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Immunological Applications

Monoclonal antibodies bind:

Monoclonal antibody originates from unique genetic event where one developing B cell successfully completed VDJ recombination on heavy chain locus chromosome 14 mediated by RAG1/2 recognition of recombination signal sequences, non-homologous end joining with TdT adding N nucleotides creating unique complementarity determining region three loop that dominates antigen contact, plus VJ recombination on light chain locus producing paired variable domains. All progeny via mitosis carry identical nucleotide sequence encoding paratope whose three-dimensional shape, electrostatic surface, and hydropho

Ref: Abbas Cellular Molecular Immunology 10th ed monoclonal single epitope uniform affinity; Roitt Essential Immunology specificity.

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Immunological Applications

Monoclonal antibodies bind:

Bevacizumab recombinant humanized IgG1 mAb 149 kDa neutralizes soluble VEGF-A isoforms 121 165 189 206 secreted tumor stromal inflammatory cells hypoxia HIF1alpha binding hypoxia response elements driving transcription. VEGF-A binds VEGFR1 FLT1 and R2 KDR tyrosine kinases endothelial cells dimerization autophosphorylation Tyr1175 recruiting PLC gamma generating IP3 DAG increasing calcium PKC stimulating proliferation permeability via VE-cadherin internalization gaps survival Akt phosphorylation caspase-9. Binding epitope Arg82 Lys84 affinity 0.5 nM overlapping receptor binding interface preven

Ref: Ferrara NEJM Bevacizumab VEGF Targeted Therapy 2004; FDA Avastin Mechanism Label VEGF Neutralization; Lodish Angiogenesis VEGF Signaling Pathway Chapter 23.

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PCR

Which PCR component gives specificity?

Specificity in polymerase chain reaction arises primarily from sequence complementarity between primers and template. Each primer of 18-22 bases is designed to anneal uniquely to flanking regions of target locus under stringent annealing temperatures, thereby defining start and end of amplicon. dNTPs are generic building blocks, polymerase catalyzes extension indiscriminately, and template provides coding information but does not select region. Well-designed primers with unique sequences, appropriate GC content, and avoidance of repeats prevent mispriming, non-specific bands, and genomic cross

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Flow cytometry, FACS, ELISA

Which enhances ELISA sensitivity without compromising specificity?

Sensitivity in ELISA often enhanced via avidin biotin system without losing specificity. Primary antibody binds antigen, biotinylated secondary antibody binds primary, then streptavidin conjugated enzyme with four biotin binding sites attaches. Each secondary can carry multiple biotins, recruiting many enzyme molecules, amplifying signal dramatically. HRP and ALP alone give single enzyme per antibody. Direct detection lacks amplification steps. Biotinylation preserves antibody specificity because antigen recognition remains unchanged, while enzyme loading increases. This approach lowers detect

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Microscopy

Which of the following enhances ELISA sensitivity without affecting specificity?

Signal amplification without compromising antigen recognition can be achieved through biotin-streptavidin chemistry. Secondary antibody conjugated to biotin retains full binding specificity for primary antibody Fc region, but each biotin can recruit tetrameric avidin coupled to multiple enzyme molecules. This creates a lattice multiplying enzyme copies per immune complex, boosting substrate conversion and lowering detection limit. Because primary antigen-antibody affinity remains unchanged, background does not rise appreciably. Simply adding more antigen, using unlabeled antibody or increasing

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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