NEET Practice Questions (MCQs) with Answers & Solutions

The NCERT text mentions, 'Using, the kinetic theory of gases, the bulk measurable properties like viscosity, heat conductivity and diffusion can be related to the microscopic parameters like molecular size. It is through such relations that the molecular sizes were first estimated.' This highlights the role of kinetic theory, and particularly concepts like mean free path, in connecting the macroscopic and microscopic worlds.

The context clearly states, 'Figure 9.6 Polymerase chain reaction (PCR) : Each cycle has three steps: (i) Denaturation; (ii) Primer annealing; and (iii) Extension of primers'. Therefore, the correct sequence is Denaturation, Annealing, Extension.

The excerpt states, 'multiple copies of the gene (or DNA) of interest is synthesised in vitro'. 'In vitro' means 'in glass' or in a test tube, distinguishing it from processes occurring 'in vivo' (within a living organism).

The text explicitly states under the heading '9.3.3 Amplification of Gene of Interest using PCR': 'In this reaction, multiple copies of the gene (or DNA) of interest is synthesised in vitro'. This is the primary purpose.

The text states, 'PCR is now routinely used to detect HIV in suspected AIDS patients'. It also mentions detecting mutations in suspected cancer patients and other genetic disorders.

The text explains, 'However, very low concentration of a bacteria or virus... can be detected by amplification of their nucleic acid by PCR.' This ability to amplify even minute amounts of genetic material makes early detection possible.

The text states, 'The sensitivity of the technique has been increased by use of polymerase chain reaction (PCR...). Consequently, DNA from a single cell is enough to perform DNA fingerprinting analysis.'

The section on PCR focuses on 'synthesised in vitro using two sets of primers and the enzyme DNA polymerase'. DNA ligase is used for 'joining of DNA' to prepare recombinant DNA, which is a separate step before or after amplification, but not directly part of the PCR amplification cycle itself.

The text mentions, 'It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful technique to identify many other genetic disorders.'

While the specific temperature isn't mentioned for denaturation, it's a fundamental step of PCR to separate DNA strands. Denaturation usually involves high temperatures to break hydrogen bonds, making the single strands available for primer annealing. This is implied by the order of steps (Denaturation, then Annealing).