Select all the of the statements below that apply to both eukaryotic and bacteri

Question

Select all the of the statements below that apply to both eukaryotic and bacterial gene expression?

A. Bacteria and eukaryotes have 70S ribosomes in their cytoplasm.

B.   Bacteria and eukaryotes can have 70S ribosomes.

C.   Bacterial and eukaryotic mRNA is modified prior to translation.

D.   Initiation of translation in bacteria and eukaryotes occurs when the ribosomal subunit binds to the 5' guanine cap.

E.   Bacteria and eukarytoes may have genes organized and regulated within operons.

A. Bacteria and eukaryotes have 70S ribosomes in their cytoplasm.

B.   Bacteria and eukaryotes can have 70S ribosomes.

C.   Bacterial and eukaryotic mRNA is modified prior to translation.

D.   Initiation of translation in bacteria and eukaryotes occurs when the ribosomal subunit binds to the 5' guanine cap.

E.   Bacteria and eukarytoes may have genes organized and regulated within operons.

Explanation / Answer

e. Bacteria and eukaryotes may have genes organised and regulated within operons

In bacterial cells as well as in chloroplasts of higher plants, sedimentation coefficient of complete ribosomes is 70S, that of smaller subunit is 30S and that of bigger subunit is 50S. In higher organisms, sedimentation coefficient of ribosomes is 80S and those of subunits are 40S and 60S. The ribosomes in mitochondria of higher organisms vary in size. In plant mitochondria, they are only little smaller than the ribosomes in surrounding cytoplasm (in maize mitochondria, 78S), In mitochondria of lower eukaryotes (e.g. fungi), these are slightly larger than in E.coli (73S in yeast), and in mammalian mitochondria they are much smaller (60S in Xenopus and human mitochondria).

Protein coding structural genes in higher eukaryotes are transcribed in the nucleus, but the RNA transcript in the nucleus differs from mRNA used for translation in the cytoplasm. This RNA transcript in the nucleus, due to its broad size distribution (500-20,000 bp) is called heterogenous nuclear RNA (hnRNA) and is much larger than its corresponding mRNA. RNA processing steps include (i) Modification of 5' end by capping and modification of 3' end by a tail (polyadenylation) after enzymatic cleavage (ii) splicing out of intron sequeces from RNA transcripts of interrupted genes.

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