Question

Place the steps in their proper order on the figure to complete the summary of gene expression in a eukaryotic cell.

Answer 1

According to the theory of central dogma, mRNA is synthesized by transcription of the coding sequence of DNA in the nucleus. As the nascent mRNA moves out of nucleus, it reaches the rough endoplasmic reticulus and hence the ribosomes. Here, the closely coupled activity of the tRNA, codon complementarity and initiation of the translation play a critical role in synthesis of appropriate amino acids from the mRNA. The whole process is regulated at very steps and is of very high accuray and fidelity.

Thus, the correct order of events can be summarized as below:

1. DNA in nucleus serves as template.
2. Pre-mRNA is processed before leaving from nucleus.
3. mRNA moves from nucleus reaches the cytoplasm and gets associated with ribosomes.
4. tRNA with anticodons carry amino acids on mRNA.
5. Codon-anticodon base pair complementarity takes place
6. Polypeptide synthesis takes place at one amino acid at a time.
7. When ribosome attaches the ER, the polypeptide enters the lumen where polypeptide folds and undergoes further modifications.
8. At termination, the ribosome detaches from ER and ribosomal subunits and mRNA dissociate.

Thus, the above given order of events describe the process of transcription, translation and post-translational modifications.