Explanation: Five unusual bases, produced by enzymatic modification of the usual bases, may be observed in a tRNA molecule. These are pseudouridine, dihyrdouridine, hypoxanthine, thymine and methylguanine. Of these five, unusual bases pseudouridine and dihyrdouridine are most commonly found in the tRNA molecules.

Explanation: For recombination to occur, the R2 segment of the Trp DNA molecule must recombine with R3 segment of the bottom DNA molecule. R1 segment of the top molecule must recombine with R4 segment of the bottom DNA molecule.

Explanation: In the process of homologous recombination, DNA molecules are regenerated by the process of genetic exchange. This is known as the process of resolution.

Explanation: In nucleotide excision repair complex of two UvrA and UvrB molecules scan the DNA with two UvrA subunits being responsible for detecting the distortions to the helix. Upon encountering a distortion, UvrA exits the complex and create a single stranded bubble with UvrB.

Explanation: cDNA library lacks DNA fragments from the genomic DNA. This type of library is produced by the action of reverse transcriptase on the mRNA molecule to synthesize complementary DNA molecules without the intervening introns.

Explanation: Genetic, biochemical and X-ray crystallographic evidence indicate that the specificity determinants are clustered at the two distant sites on the molecule. They are the acceptor stem and the anticodon loop.

Explanation: The nucleotides are known to be enzymatic molecules. For example, ribozymes are catalytic molecules. Also certain derivatives of nucleotides such as ATP, coenzyme A, nicotinamide adenine dinucleotide, etc., are important catalytic molecules that participate in various enzymatic processes.

Explanation: Nucleic acids, that is, DNA and RNA show phosphodiesterase linkage which is the major type of linkage. Without the phosphodiester bonds between the phosphate and adjacent 3’OH sugar molecule the backbone will not be formed. Therefore, the nucleotides would not be able to attach and bond to form a nucleic acid.

Explanation: Ethidium bromide only helps in tagging the DNA molecules to make the visible under the UV radiation due to its fluorescence property, but does not take any part in the separation of DNA molecules during electrophoresis.

Explanation: The speed of DNA replication that is, 200 to 1000 nucleotides per second. Translation takes place at a rate of only 2 to 20 amino acids per second.

Explanation: Mutation facilitates the change of bases within a DNA and if this change encodes for a viable amino acid which in turn may lead to the synthesis of a different protein. This protein exerts a phenotypic character to the organism which may be different from the wild type character or may generate a unique character itself, thus leading to evolution.

Explanation: A nucleic acid backbone is mainly composed of a pentose-phosphate unit which acts as a monomer. The repeat of this monomer is attached together by the phosphodiesterase linkage, thus, giving rise to the backbone. The nucleotides attached to the sugar moieties forms the side chain which gives rise to the hydrogen linkage with its complementary strand.

Explanation: Replication is the coping of the gene in double but plays no role in the production of protein thus, expression of gene. Transcription is the production of RNA from DNA and RNA processing is used for stabilizing the RNA in cytosol ad excision of non-coding regions. Translation is the major process that leads to the formation of polypeptide chain.

Explanation: Exons are the part of nascent RNA that are connected together to form RNA after the removal of introns by the splicosome. The splicosome in the complex formed in the nucleus with nascent RNA being the substrate for the formation of mature RNA after its splicing and other post transcriptional mechanisms.