Question

Describe the features of the gene organization and the gene structure between bacteria and human. How do these differences of genomic features provide evolutionary adaptations to prokaryotic and eukaryotic organismal functions.

Answer 1

Deoxyribonucleic acid (DNA) sequences from human chromosomes and chromosomes of other organisms are enabling a detailed look at the structure and organization of protein‐coding information in the context of genomes as a whole. Groups of genes can now be examined in relation to broader landscape features such as the guanine plus cytosine (G+C) content, interspersed genome‐wide repeats and syntenic relationships between species.

The Difference Between Bacterial Cell and Human Cell are quite few yet very significant.

Difference Between Bacterial Cell and Human Cell

Differences in	Bacterial cell	Human cell
Cell	Cell is isolated and Independent. It survives as an individual on its own.	Human cells are in a group and not isolated. It is dependent on other cells for survival.
Cell wall	Thick protective cell wall is present covering the whole cell.	The wall is absent
Cell membrane is made of	Is made of phospholipid bilyaer. But the memebrance lacks sterols.	Lipid bi-layer with phosphate molecules. It is hydrophilic to external and hydrophobic in the inner wall.
Cell membrane has	No cytoplasmic bridges as there is only one cell.	Cytoplasmic bridges are present which help in inter-cellular transport in between neighboring cells.
Cell shape	Cells can be of different shapes	Only spherical or oval
Cell appendages (External parts)	Present. Flagella for movement, pili for sexual reproduction.	Absent mostly. Except for ciliated cells in respiratory tract & gut.
Nucleus	Nucleus is Absent. Instead nuclear content like DNA are present in cytoplasm. No distinct nucleus, so called as prokaryote	Prominent nucleus with nuclear membrane. So called as an eukaryote type.
DNA synthesis & Elongation	Enzyme DNA Gyrase is involved.	Enzyme Topoisomerase is involved
RNA (ribo nucleic acid)	70 s type with 50s and 30s type sub units.	80 s type with 60 s and 40 s sub units.
Capsule (a form of inactive cell)	Bacterial cell under goes to form capsule which is resistant to harsh condition of drought and temperature. Can give back live bacteria in good conditions.	Absent
Cell death	Bacterial cell is immortal. It never dies unless subjected to sterilization. Divides for new offspring’s. Even in harsh conditions it tries to survive as spore form (dormant)	Human cell is mortal. Cell dies by either apoptosis or necrosis.
Nutrition	Autotrophic, heterotrophic, parasitic etc. Autotrophs manufacture their own food. Disease causing bacteria are parasites & live on other organisms.	Heterotrophs. Depends on the food supplied by blood from body gut.
Reproduction	Both sexual and asexual reproduction happens	Asexual reproduction only.
Cell division occurs by	Mitosis and meiosis. Mitosis gives two cells and meiosis gives fur cells	All cells undergo mitosis. Only ovum and sperm formation by meiosis. While nerve cells never divide.
Movement	Can move on their own with flagella for normal needs.	Cannot move, except for sperm and ova. While blood cells flow in the fluid.

Also, there are variations like, the bacteria are immortal creatures, i.e., they do not die as such except under harsh conditions.

They are quite primitive living organisms on the earth and are of various types. On the other hand, a human is an advanced living being.

As you might have heard before, they cause various diseases to humans. But there are also friendly and useful bacteria.

They are single-celled organisms and yet that single cell can perform all of its functions.

These differences are the key to the treatment of bacterial diseases by use of antibiotics.

Bacteria cell with cell components like the chromosomes, pilus, flagella, ribosomes, plasmids, etc.

Without such differences, it would be difficult to target and kill bacterial cells once they get into the human body.

The difference between a bacterial cell and human cell help us fight bacterial infections. Antibiotics when administered, into the human body act in such a way that only bacterial cells are killed while sparing humans.

Some of the common targets to achieve this safe drug action are the cell wall, 70s ribosomes, DNA gyrases, etc.

The main difference between prokaryotic and eukaryotic gene structure is that the prokaryotic gene structure consists of operons and clusters of several functionally-related genes, whereas the eukaryotic gene structure does not contain operons. Furthermore, the introns present in the eukaryotic gene structure interrupts the open reading frame while there are no introns in the prokaryotic gene structure.

Prokaryotic and eukaryotic gene structure are two types of gene structures with different organizations. Both undergo transcription and translation to produce functional proteins.

Eukaryotes

The structure of eukaryotic genes includes features not found in prokaryotes. Most of these relate to post-transcriptional modification of pre-mRNAs to produce mature mRNA ready for translation into protein. Eukaryotic genes typically have more regulatory elements to control gene expression compared to prokaryotes. This is particularly true in multicellular eukaryotes, humans for example, where gene expression varies widely among different tissues.

A key feature of the structure of eukaryotic genes is that their transcripts are typically subdivided into exon and intron regions. Exon regions are retained in the final mature mRNA molecule, while intron regions are spliced out (excised) during post-transcriptional processing. Indeed, the intron regions of a gene can be considerably longer than the exon regions. Once spliced together, the exons form a single continuous protein-coding regions, and the splice boundaries are not detectable. Eukaryotic post-transcriptional processing also adds a 5' cap to the start of the mRNA and a poly-adenosine tail to the end of the mRNA. These additions stabilise the mRNA and direct its transport from the nucleus to the cytoplasm, although neither of these features are directly encoded in the structure of a gene.

Prokaryotes

The overall organisation of prokaryotic genes is markedly different from that of the eukaryotes. The most obvious difference is that prokaryotic ORFs are often grouped into a polycistronic operon under the control of a shared set of regulatory sequences. These ORFs are all transcribed onto the same mRNA and so are co-regulated and often serve related functions. Each ORF typically has its own ribosome binding site (RBS) so that ribosomes simultaneously translate ORFs on the same mRNA. Some operons also display translational coupling, where the translation rates of multiple ORFs within an operon are linked. This can occur when the ribosome remains attached at the end of an ORF and simply translocates along to the next without the need for a new RBS.Translational coupling is also observed when translation of an ORF affects the accessibility of the next RBS through changes in RNA secondary structure. Having multiple ORFs on a single mRNA is only possible in prokaryotes because their transcription and translation take place at the same time and in the same subcellular location.

The operator sequence next to the promoter is the main regulatory element in prokaryotes. Repressor proteins bound to the operator sequence physically obstructs the RNA polymerase enzyme, preventing transcription.Riboswitches are another important regulatory sequence commonly present in prokaryotic UTRs. These sequences switch between alternative secondary structures in the RNA depending on the concentration of key metabolites. The secondary structures then either block or reveal important sequence regions such as RBSs. Introns are extremely rare in prokaryotes and therefore do not play a significant role in prokaryotic gene regulation.