NEET Practice Questions (MCQs) with Answers & Solutions

I is correct because 'globules unfold and helix get uncoiled' affecting overall folding (tertiary and secondary structures). II is incorrect because the primary structure (amino acid sequence) remains intact. III is incorrect because hydrogen bonds are 'disturbed', not strengthened.

Denaturation is caused by changes in temperature or pH that disturb hydrogen bonds. Maintaining optimum conditions (temperature and pH) is where a protein exhibits its highest activity and is least likely to denature. Extremes of temperature and pH (like strong acids/bases leading to extreme pH) cause denaturation.

The NCERT text states, 'RNAi takes place in all eukaryotic organisms as a method of cellular defense.'

The NCERT book mentions, 'A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield.' This highlights the specific target of the nematode.

The NCERT text states, 'This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).'

According to the NCERT text, the dsRNA 'binds to and prevents translation of the mRNA (silencing).'

The context clearly states, 'Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant...'

The NCERT text explains, 'The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells.' These then form dsRNA.

The NCERT states, 'The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA.'

The NCERT text provides, 'The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.'