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#lab techniques

27 public questions tagged with this topic.

ZOOLOGY

Which of the following best describes gel electrophoresis?

Gel electrophoresis is used to separate DNA fragments based on size using an electric field. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Zoology section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Zoology portion (Latest NCERT Textbooks for Academic Session 2026-27 - Rationalized Edition for Class XI and XII), Topic: Structural organization, ph

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Animal Tissue Culture 1

Protease inhibitors are added to prevent:

Innate immunity balances protease mediated tissue remodeling with protective antiproteases preventing autodamage. Neutrophils recruited to injury sites degranulate releasing azurophilic granules containing serine protease neutrophil elastase capable of degrading elastin collagen, cathepsin G, proteinase 3, and specific granules releasing matrix metalloproteases MMP8 collagenase and MMP9 gelatinase facilitating migration through basement membrane. Uncontrolled release would destroy cartilage and lung parenchyma causing emphysema in alpha-1 antitrypsin deficiency. Plasma contains defensive inhib

Ref: Lodish Molecular Cell Biology serpin α1 antitrypsin α2 macroglobulin; Alberts MBoC protease inhibitors serum protection lysis cocktail.

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Immunological Applications

Agglutination reactions are based on:

Agglutination depends multivalent antibody capable crosslinking particulate antigens particles larger soluble proteins into large aggregates visible macroscopically naked eye low magnification facilitating rapid low-cost diagnostics bedside. IgM pentameric 900 kDa ten Fab arms arranged star shape span 30 nm ideal bridging IgG bivalent two Fab flexible hinge enabling simultaneous binding distinct particles. Antigen presents repetitive surface array ABO blood group antigens A trisaccharide GalNAc alpha1-3(Fuc alpha1-2)Gal B Gal alpha1-3(Fuc alpha1-2)Gal erythrocyte glycophorin bacteria O lipopol

Ref: Janeway Immunobiology Agglutination Mechanism Chapter 14 Lattice; NCBI Clinical Microbiology Agglutination Tests Principles; Alberts Antigen-Antibody Lattice Formation Theory Kinetics.

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Immunological Applications

RIA stands for:

Radioimmunoassay RIA competitive binding assay pioneered Berson Yalow 1960 Nobel Prize Medicine 1977 enabled first quantification peptide hormones insulin glucagon pg concentrations revolutionizing endocrinology. Principle relies limited antibody binding sites fixed high-affinity polyclonal antibody specific analyte insulin 51 aa thyroxine T4 triiodothyronine growth hormone 191 aa incubated known quantity iodine-125 labeled antigen purified chloramine T oxidizing iodide iodine incorporating tyrosine achieving specific activity 50-100 uCi per ug variable unknown unlabeled sample antigen competi

Ref: Yalow and Berson 1960 RIA J Clin Invest Nobel Method; NCBI StatPearls Radioimmunoassay Principles https://www.ncbi.nlm.nih.gov/books/NBK557486/; Janeway RIA Technique Immunoassay Chapter 3.

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DNA & RNA isolation

What is the emission wavelength of EtBr when bound to DNA?

Ethidium bromide is a fluorescent intercalator whose photophysics change dramatically upon DNA binding. Free EtBr in aqueous solution emits weakly, but when intercalated between base pairs, hydrophobic environment shields it and fluorescence quantum yield increases about 20-fold. Upon excitation with UV around 302 nm or 365 nm, the DNA-EtBr complex emits orange-red fluorescence with emission maximum near 590 nm. This property enables visualization of DNA bands in agarose gels under UV transilluminator. Shorter wavelengths like 260 nm or 400 nm are absorption peaks, not emission maxima.

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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DNA & RNA isolation

Which of the following is used to quantify DNA using fluorescence?

Fluorescent quantification of DNA employs DNA-binding fluorochromes for sensitivity beyond UV absorbance. SYBR Green I is a cyanine dye that exhibits extremely low fluorescence when free but over 1000-fold enhancement upon intercalation into minor groove of double-stranded DNA. This allows specific quantitation of dsDNA even with contaminants present. Coomassie Blue stains proteins, DAPI binds AT-rich dsDNA but is used mainly for microscopy, and TRIS is a buffer. SYBR Green is standard for real-time PCR quantification and fluorometric assays with high specificity and linearity.

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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