(1)

(4)

(4)

In transcription unit, the promoter and terminator flank the structural gene. The promoter is said to be located towards 5′-end (upstream) of the structural gene and the terminator towards the 3′-end (downstream) of the coding strand.

(3)

(4)

RNA polymerase III is responsible for transcription of tRNA, 5SrRNA and snRNAs (small nuclear RNAs). RNA polymerase I transcribes rRNA (28S, 18S and 5.8S) whereas RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).

(1)

(3)

(3)

Split gene arrangement is a characteristic of eukaryotes. In capping, an unusual nucleotide (methyl guanosine triphosphate) is added to the 5′-end of hnRNA. RNA polymerase binds with termination factor Rho ($\mathrm{\rho }$) to terminate the process of transcription in bacteria. The coding strand does not code for anything.

(3)

In bacteria, there is a single DNA dependent RNA polymerase that catalyses transcription of all types of RNA. It associates transiently with initiation factor ($\mathrm{\sigma }$) and termination factor ($\mathrm{\rho }$) to carry out initiation and termination of transcription respectively. It catalyses the elongation as its uses nucleoside triphosphates as substrates and polymerises in a template dependent fashion as rule of complementarity.

(4)

(2)

(3)

(2)

Franklin Stahl along with Matthew Meselson proved semi-conservative mode of replication in DNA. Punnett square was developed by a British geneticist, Reginald C. Punnett. Spliceosome formation is part of post-transcriptional change in eukaryotes. Transduction was discovered by Joshua Lederberg and Norton Zinder in the bacterium Salmonella.

(1)

Coding strand and mRNA have same nucleotide sequence except, ‘T’ – Thymine is replaced by ‘U’ – Uracil in mRNA.

(4)

rRNA (ribosomal RNA) is the most abundant of all types of RNA (70–88%). Hence, it will be present in highest amount. Percentage of tRNA and mRNA is 15% and 2–5% respectively. miRNA (micro RNA) are 21–22 bp long RNA that bring degeneration of mRNA.

(3)

Spliceosomes help in removal of introns. They will not occur in prokaryotes because prokaryotes do not have introns and thus, processing does not require splicing of mRNA.

(2)

Cistron (or gene) is a length of DNA that contains the information for coding a specific polypeptide chain or a functional RNA molecule (i.e., transfer RNA or ribosomal RNA). Hence, cistron is a unit of function. Currently such a gene is called structural gene.

(3)

23S rRNA acts as structural RNA as well as ribozyme in bacteria.

(1)

The strand of DNA on which RNA polymerase binds to catalyse transcription is called template strand. It is also known as master or antisense strand. It has the polarity of 3′ → 5′.

(1)

RNA polymerase initiates and extends the RNA (chain elongation) and functions always in 5′ to 3′ direction. The structural component of DNA has 3′ to 5′ polarity. It is also called template DNA strand or antisense (–) strand.

(2)

The process of copying genetic information from one strand of the DNA into RNA is known as transcription. It occurs in the cytoplasm with the help of transcripting enzyme.

Transport of pre-mRNA to cytoplasm prior to splicing is a part of transcription.

The primary transcript is converted into functional mRNA after post transcriptional processing involves 3 steps as follows-

•   Modification of 5’ end by capping,

•   Tailing,

•   Splicing.

Base pairing of two complementary RNA is not on event of post-transcription. Hence, statements B, C, D are post-transcriptional modification events in eukaryotic cell.

(3)

In prokaryotes the RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation factor ($\sigma$) and termination factor ($\rho$) to initiate and terminate the transcription respectively.