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DIFFERENCES IN PROTEIN SYNTHESIS IN PROKARYOTES AND EUKARYOTES

Fig.8.17
Fig 8.17 Differences in protein synthesis in prokaryotes and eukaryotes

S.No.

Eukaryotes

Prokaryotes

1.

In eukaryotes many genes are split genes (containing exons and introns) that after transcription give rise to hnRNA molecules, which are longer than the actual mRNA. This hnRNA, after splicing of introns gives rise to the mRNA that contains the right information of the protein synthesized from it (exons). In all prokaryotes the mRNA synthesized corresponds exactly the length of the concerned protein.

2.

During processing, a 7mG cap at 5’ and poly A tail at the 3’ end is added to give final mRNA. The mRNA does not contain such cap and tail

3.

The initiation codon is located a few nucleotides away from the 5′ end of mRNA, and during translation process the ribosome after attaching at the 5′ end, moves along the mRNA to find the initiation codon. Here, the initiation codon in mRNA lies exactly at its 5′ end.

4.

Since, the chromosomes containing DNA are separated from the cytoplasm by the nuclear membrane, transcription occurs in nucleus and translation in cytoplasm. Thus, transcription and translation processes occur separately at different time periods. The transcription and translation processes occur almost simultaneously ill the cytoplasm due to the absence of a nuclear membrane

5.

Ribosomes involved in translation process in the cytoplasm are of 80S type, whereas, in organelles, mitochondria and chloroplasts they are generally of 70S type. 70S type ribosomes are involved in the translation process.

 

QUESTIONS

1.Write short notes on:

 i.Two dimensional structure of tRNA

 ii. Extended anticodon hypothesis

 iii. Central dogma

 iv. Reverse transcription

v.RNA polymerases

 vi.Promoter sites

 vii.Modification of released polyopeptide

 viii. Initiation of protein synthesis (translation)

 ix. Ribosomes

 x. Differences in protein synthesis of prokaryotes and eukaryotes.

2.Discuss the termination of mRNA in prokaryotes.

3.Write a note on termination and maturation of mRNA in eukaryotes.

4.Give an account of the mechanism of protein synthesis (translation) in prokaryotes.

5. Discuss the protein synthesis (translation) in eukaryotes.