#cell sorting

Flow cytometry, FACS, ELISA

What is the use of flow cytometry?

Flow cytometry analyzes physical and chemical properties of individual cells suspended in fluid. Hydrodynamic focusing forces single file passage through laser intercept, measuring forward scatter proportional to size, side scatter indicating granularity, and fluorescence from labeled antibodies or dyes reflecting antigen expression, DNA content or calcium flux. It does not sequence DNA, assess protein tertiary folding or amplify nucleic acids like PCR. Applications include immunophenotyping, cell cycle analysis, apoptosis detection, sorting of specific populations for culture, making it powerful for quantitative cellular property measurement.

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

Who developed flow cytometry?

Flow cytometry evolved from principles of Coulter volume sensing and fluorescence detection of single cells in fluid stream. Mack Fulwyler in 1965 described the first fluorescence based cell sorter separating cells by volume, publishing electrostatic deflection principle that became foundation of modern instruments at Los Alamos. Engvall and Perlmann developed ELISA methodology, Rosalyn Yalow pioneered radioimmunoassay for insulin measurement. Fulwyler innovation enabled hydrodynamic focusing, laser interrogation and charged droplet sorting, allowing quantitative analysis of size, granularity and fluorescence at thousands of cells per second.

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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Cell Communication and Cell Adhesion

Cell sorting during embryogenesis is best explained by

Differential adhesion hypothesis, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Communication and Cell Adhesion

Cadherin-mediated cell sorting during development depends on

Differential cadherin expression levels, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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