Quaternary- Extinctions of large mammals, and birds; evolution of Homo sapiens, spread out of Africa

TLS Online TPP Program

#Id: 4628

#Unit 13. Methods in Biology

Enzyme-linked immunosorbent assay, commonly known as ELISA (or EIA), is similar in principle to RIA but depends on an enzyme rather than a radioactive label. 

TLS Online TPP Program

#Id: 4629

#Unit 13. Methods in Biology

A number of enzymes have been employed for ELISA, including alkaline phosphatase, horseradish peroxidase, and -galactosidase. These assays approach the sensitivity of RIAs and have the advantage of being safer and less costly.

TLS Online TPP Program

#Id: 4630

#Unit 13. Methods in Biology

 Antigen can be detected or measured by a sandwich ELISA .In this technique, the antibody (rather than the antigen) is immobilized on a microtiter well. 
A sample containing antigen is added and allowed to react with the immobilized antibody. After the well is washed, a second enzyme- linked antibody specific for a different epitope on the antigen is added and allowed to react with the bound antigen
After any free second antibody is removed by washing, substrate is added, and the colored reaction product is measured.

TLS Online TPP Program

#Id: 4631

#Unit 13. Methods in Biology

Competitive ELISA. In this technique, antibody is first incubated in solution with a sample containing antigen. The antigen-antibody mixture is then added to an antigen coated microtiter well.
The more antigen present in the sample, the less free antibody will be available to bind to the antigen-coated well. 
Addition of an enzyme-conjugated secondary antibody (Ab2) specific for the isotype of the primary antibody can be used to determine the amount of primary antibody bound to the well as in an indirect ELISA. 
In the competitive assay, however, the higher the concentration of antigen in the original sample, the lower the absorbance.

TLS Online TPP Program

#Id: 4632

#Unit 13. Methods in Biology

 What are the principles in flow cytometry?

• Light scattered by a laser or arc lamp

• Specific fluorescence detection

• Hydrodynamically focused stream of particles

• Electrostatic particle separation for sorting

• Multivariate data analysis capability

TLS Online TPP Program

#Id: 4633

#Unit 13. Methods in Biology

3H thymidine uptake assays were the first to be used routinely to measure cell division in lymphocyte cultures