Question

4. In class, we discussed that regulation of gene expression in eukaryotes and prokaryotes have some similarities and some differences. I want you to focus on what's different between these two type of cells: name TWO mechanisms of control of gene expression that are only used by eukaryotes and discuss why each of those mechanisms wouldn't be possible in prokaryotes. [4 pts]

Detailed explanation plz.

Answer 1

Gene regulation occurs in both prokaryotes and eukaryotes. In both regulation occurs during the process of transcription.

But, in prokaryotes, genes are arranged as operons. Group of genes are arranged in to a linear structure called operons. This unit has both structural and regulatory parts in DNA, In eukaryotes, genes are not arranged in operons. Each gene has a different promoter. So every gene has to be regulated separately by using inhibitors. In case of prokaryotes, because genes are arranged as groups, one promoter can control the transcription of many genes. But in both cases, repressor molecule can control the transcription in the similar manner.

Another way that can be very commonly seen in eukaryotes is by acetylation and methylation. DNA is coiled around histone proteins in eukaryotes. When the DNA is coiled, it cant transcribe as its genes are not accessible. where as uncoiled DNA can be transcribed. So this advantange is taken for regulation of genes in Eukaryotes. Acetylation of the histone proteins will uncoil the DNA, allow transcription. Where deacetylation will make DNA coil tightly around histone octamers and prevent transcription.

Methylation of the histone proteins will make DNA coil more tightly and demethylation will allow DNA to loosen form the coils. CpG islands are hotspots for DNA methylation. So this is another way of gene regulation. Since Eukaryotes do not have arrangements as operons, they have a different mechanism for gene regulation.

Eukaryotes also regulate genes post trasnccriptionally. Addition of capping and tailing at the 5' and 3' ends of the mRNA, removal of introns from the mRNA can all be steps for gene regulation in eukaryotes which are not found in prokaryotes as they do not have introns.

RNA i (RNA interference) is another method of gene regulation. It occurs post transcriptionally in both prokaryotes and eukaryotes.

In general eukaryotic gene regulation is more complex than the prokaryotic gene regulation. Eukaryotes have number of upstream regulatory regions which have binding sites for activators and inhibitors playing regulatory role.

So methylation and acetylation can be used only in eukaryotes and splicing of the mRNA for removing introns also can't be used in prokaryotes as they have no introns in their mRNA.