ICAR AIEEA PG 2024 - Animal Biotechnology

Viral RNA molecules (such as double-stranded RNA replication intermediates or 5'-triphosphate single-stranded RNA) serve as pathogen-associated molecular patterns (PAMPs) that induce Type I interferons (IFN-alpha/beta), which mount a powerful innate immune defense against RNA viruses.

For a linear DNA molecule, cutting at $n$ internal restriction sites generates $n + 1$ fragments. With $n = 7$ internal cleavage sites, the number of fragments produced is $7 + 1 = 8$ fragments.

A Bacterial Artificial Chromosome (BAC) is an engineered plasmid based on the E. coli fertility plasmid (F-factor). It stably clones large DNA inserts typically in the range of 100 to 300 kb (100,000 to 300,000 base pairs). Larger fragments exceeding 1 Mb require Yeast Artificial Chromosomes (YACs).

A shuttle vector is engineered with two different origins of replication and selection markers compatible with two distinct host systems (e.g., E. coli and yeast/mammalian cells), enabling it to replicate and propagate in both. Thus, Reason (R) correctly explains Assertion (A).

Native double-stranded DNA exhibits lower UV absorbance at 260 nm due to base stacking (hypochromicity). When heated, thermal energy disrupts hydrogen bonding and base stacking, converting dsDNA into single-stranded denatured DNA. This unstacking of aromatic purines and pyrimidines increases absorbance at 260 nm (hyperchromic effect). Thus, Reason (R) is the correct explanation of Assertion (A).