Question

Assertion :PCR can detect very low amounts of DNA and is now routinely used to defect HIV in suspected AIDS patient.
Reason: PCR is a powerful technique to identify many other genetic disorders.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Polymerase chain reaction (PCR) has many applications in medicine.

This is a very sensitive test that is used to amplify trace amount of DNA or RNA located in or on any liquid or any surface where DNA strand can be deposited.

The HIV is difficult to target and eradicate. Earlier tests relied on presence of antibodies to the virus in the blood. But they appear late and maternal antibodies mask the infection in newborn. PCR test can detect as little as one viral genome among the DNA of over 50,000 host cells. Suspected cases can be detected earlier, donated blood can be screened directly for the virus, newborns can be immediately tested for infection and treatment can be quantified.

PCR was first used for genetic testing. A sample of DNA was used for the presence of genetic disease mutations. PCR can be used to amplify the sequence that contains mutation with appropriate restriction enzymes, generating 10 million copies. The copies are used for further testing like endonuclease digestion with electrophoresis, hybridization to oligonucleotide probes, polymorphism analysis etc. Prospective parents can be tested for being genetic carriers in hemophilia, thalassemia. A child can be detected for actual disease. PCR analysis is also essential to preimplantation genetic diagnosis, where individual cells of developing embryo are tested for the mutation. Thus, the correct answer is option B.