Question

Describe and explain the mechanisms in which DNA is used to generate protein. In addition, identify and explain any major differences between the mechanisms in prokaryotic and eukaryotic cells.

Answer 1

The genes in DNA encode protein molecules, which are the "workhorses" of the cell, carrying out all the functions necessary for life. In the simplest sense, expressing a gene means manufacturing its corresponding protein, and this multilayered process has two major steps. In the first step, the information in DNA is transferred to a messenger RNA (mRNA) molecule by way of a process called transcription. During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase II catalyzes the formation of a pre-mRNA molecule, which is then processed to form mature mRNA (Figure). The resulting mRNA is a single-stranded copy of the gene, which next must be translated into a protein molecule.

Difference between protein synthesis in eukaryotic and prokaryotic are mentioned in below table:

Eukaryotic protein synthesis	Prokaryotic protein synthesis
Protein synthesis occurs in the cytoplasm	Protein synthesis began even before the transcription of mRNA molecule is completed. This is called coupled transcription-translation.
Eukaryotic mRNA molecules are monocistronic, containing the coding sequence only for one polypeptide	mRNA are polycistronic containing the coding sequence of several genes of a particular metabolic.
The primary mRNA transcript undergoes processing and splicing to change into functional mRNA	Splicing of mRNA transcript does not occur.
In eukaryotes, mRNA molecules are modified by the addition of a 5'G cap formed of methylated gaunosine triphosphate	No such cap is formed at 5' end of bacterial mRNA
A poly A tail formed about 200 adenine nucleotides is added at the 3' end of mRNA	No poly A tail is added to bacterial mRNA
The first amino acid methionine entering the ribosome is not formylated	The first amino acid methionine is formylated into N formyl methionine
The pre initiation complex formation is initiated by nine initiated factors.	Only two initiating factors are involved