​Match the following bacterial gene expression mechanisms:​

​Which one of the following options represents all correct matches between Column X and Column Y?​

​Precise recognition of tRNAs by their cognate aminoacyl-tRNA synthetases is crucial for the fidelity of protein synthesis. In the context of the aminoacylation of tRNA^Ala with its cognate aminoacyl-tRNA synthetase (AlaRS), and based on the studies on the molecules of Escherichia coli origin, the following statements are made.​

​Which one of the statements is INCORRECT?​

​

​Which one of the following combinations represents the major protein or protein complex involved in chromatin condensation in yeast and human, respectively?​

​In bacteria many of the tRNA genes do not contain the CCA sequence found at the 3' end of tRNA. In this context, which one of the following statements represents the correct explanation?​

​The sequence below represents part of the coding strand of the bacterial gene Z. The arrow indicates the transcription start site:​

The following statements were made with reference to transcription & translation of the strand:
A. Insertion of an ‘A’ nucleotide after position +8 increases the length of the transcript by 1 nucleotide and changes the amino acid sequence of the protein being translated.
B. Substitution of the ‘T’ at position 22 changes the primary structure of the protein without altering transcript length.
C. Insertion of an ‘A’ after position 26 changes the primary structure of the protein and results in synthesis of a truncated protein.
D. Deletion of ‘A’ at position 9 creates the ‘STOP’ codon that prevents translation of the protein.

Which one of the options below represents the combination of all correct statements?

The 5′ UTR of ferritin mRNA forms a stem-loop structure called the iron regulatory element (IRE). The Iron Regulatory Binding Protein [IRBP] binds this IRE.
The following statements were made with reference to IRBP-IRE interaction:
A. IRBP-IRE interaction prevents eIF4A from resolving the stem-loop structure, thus preventing initiation of translation of ferritin genes.
B. IRBP-IRE interaction recruits eIF4A to the 5′ UTR, thus promoting translation initiation.
C. In presence of ferrous ions IRBP is unable to bind the IRE.
D. eIF4A binds directly at the 5′ UTR and disrupts the stem-loop structure, thus promoting translation initiation.

Which one of the options below represents the combination of all correct statements?

Following statements were made about mitochondria:
A. The D loop of the mitochondrial genome is required for replication, but not for the regulation of transcription.
B. The L strand of mitochondrial genome possesses more cytosine.
C. In plants, most mitochondrial tRNAs are encoded by the nuclear genome and then imported into the mitochondrion.
D. Cycloheximide inhibits protein synthesis by mitochondrial ribosomes, but does not affect eukaryotic cytosolic ribosomes.
E. Some organisms have been found to carry linear mitochondrial DNA.

Which one of the following options represents a combination of the correct statements?

​The amino acid arginine is encoded by six codons: CGU, CGC, CGA, CGG, AGA, and AGG. Assuming inosine is not an option in the tRNA anticodon, what is the minimum number of tRNAs that would be sufficient to read these codons?​

​The post-translational modifications in one or more core histones that are known to be associated with DNA repair pathways are:​

​Regulation of mRNA translation is a major mechanism that maintains stoichiometric availability of ribosomal proteins (r-proteins) to rRNA molecules they bind to. Translational regulation is facilitated by general occurrence of the r-protein genes in several operons containing multiple genes. Which one of the following represents an established mechanism to ensure optimal production of r-proteins in E. coli, when the r-proteins accumulate in free form (molar excess over rRNA)?​

A ‘nonsense’ mutation in the protein coding region of an upstream gene of a group of genes in an operon often leads to depletion of the downstream gene products. This is a classic example of the phenomenon of “polar effect” of the mutation. Following statements are being made about this phenomenon.

A. It occurs primarily because the termination codon generated in the upstream open reading frame (ORF) leads to termination of protein synthesis depleting the ribosomes for translation of the downstream ORFs but it does not affect the process of transcription.

B. The phenomenon of polar effects of mutation occurs only in the operons where the point mutation leading to creation of ‘nonsense’ mutation also leads to formation of a stem-loop structure resulting in Rho-independent termination.

C. While the presence of termination codon in the upstream ORF may deplete the ribosomes that travel down to the downstream ORF, the depletion of ribosomes downstream of the ‘nonsense’ mutation allows loading of the Rho factor that then results in premature transcription termination.

D. Presence of the suppressor tRNA reading the ‘nonsense’ codon generated by the mutation, is essential for causing a polar effect of the mutation.

E. Presence of the suppressor tRNA reading the ‘nonsense’ codon generated by the mutation diminishes the consequences of the polar effects.

Choose the option that represents all correct statements.