Transcription and Translation in Eukaryotes

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What are eukaryotes?

These are organisms whose cell structure such as organelles is enclosed within the membrane. The nucleus is the defining cell structure that sets eukaryotic cells apart from the prokaryotic cells. The presence of the nucleus gives these organisms their names. Being more complex than Prokaryotes, they make up all fungi, plant, animals such as amoeba.

Eukaryotic cells are known for their strong cytoskeleton and their internal membranes. The cytoskeleton is made of proteins like actin and keratin which holds a cell together, differentiating its organelles. Eukaryote means “true nut,” which implies that eukaryotic cells possess an internal nucleus while prokaryotes which means “before nut” implies that they do not have an internal nucleus. As compared to prokaryotes, Eukaryotes are more recent in history and a typical eukaryotic cell is larger than the typical prokaryotic cell.

 

Figure 1. A Typical Eukaryotic Cell

Transcription in eukaryotes

This is the process where eukaryoticcells copy the genetic formation stored in the DNA to units of RNA replica. This process is separated into transcription and translationby the nucleus. It takes place in the nucleus where the DNA is packaged into nucleosomesand higher order chromatinstructures.

Eukaryotic transcription takes place in the following precise steps. RNA polymerase and general transcription factorscombines with the promoterregion of the gene to form a closed complex referred to as the pre-initiation complex. The complex then transits from a closed to an open state. This results in the separation of the two DNA strands and the positioning of the template strand to the active site of the RNA polymerase.

Without a primer, RNA polymerase can initiate the synthesis of a RNA chain with the use of the template DNA strand, guiding the selection of ribonucleotide and the polymerisation chemistry. In some cases, the synthesis is aborted before the transcripts reach a significant length, (approximately 10 nucleotides) with the abortive cycles, short transcripts are developed by the polymerase until it is unable to generate transcripts that surpasses 10 nucleotides in length. On attainment of this threshold, RNA polymerase moves to the promoter and transcription moves to the elongation stage.

                                               Figure 2, Translation in Eukaryotes 

 

Translation in eukaryotes

This is the process whereby messenger RNA is transformed to proteins in eukaryotes. The entire process consists of initiation, elongation and termination. The ignition process involves the interaction of certain proteins with a special tag which are bound to the 5′-end of an mRNA molecule, the 5′ UTRas well as the 5′ cap. The protein behind the ribosomalsubunit also referred to as the 40Ssubunit are the initiation factorsthat holds the mRNA in place.

The eukaryotic Initiation factor 3 (eIF3) in association with the small ribosomal subunit plays the role of keeping the ribosomal subunit in form. eIF3 also interacts with the eIF4F complex which comprises of three other initiation factors: eIF4A, eIF4Eand eIF4G. eIF4G is a scaffolding protein which is associated with both eIF3 and the other two components. eIF4E is the cap-binding protein. In the end, the complete ribosome (80S) commences translation elongation during which the sequence between start and stop codons is translated from mRNA into an amino acid sequence, synthesising protein. 

By | 2014-07-18T07:59:55+00:00 January 24th, 2014|Eukaryotic Transcription, Eukaryotic Translation|0 Comments

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