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RNAs, introns and introduction to recombinant DNA.

The genome is a vault of genetic information, but on its own its kind of useless as the information cannot be used in the cell. Utilization of this information requires a coordinated effort from enzymes and proteins, this coordination of chemical reactions is known as genome expression. The initial step of genome expression is known as the transcriptome, a collection of RNA molecules which is made up of the genes active in the cell at the time. (its constantly changing to the environment that the cell is in) the transcriptome is maintained by transcription a simple process in which individual genes are copied and pasted into RNA molecules known as mRNA. The second product within gene expression  is known as proteome which you can think of as the cells library of proteins at hand. This gives the cell its unique and individual characteristics that it can express. The proteins in this library known as the proteome are synthesized by the translation of some RNA molecules.

I think it is of utmost importance to start with the most simple and important step…

Transcription:

The first step in transcription is initiation,

Transcription begins with the binding of RNA polymerase 2 to the promoter region of a gene, the most common promotor contains a conserved gene sequence we call the TATA box, but there are many others that exist which are show by the different TF families.

The next step we have the formation of transcription initiation complex, this is when transcription factors such as TATA-binding protein also known as TBP, bind to the promoter, forming a pre-initiation complex. Other general transcription factors join, and RNA polymerase 2 is recruited to form the transcription initiation complex.

Next, we have initiation of transcription where RNA polymerase 2 unwinds the DNA helix at the transcription “start site”. The enzyme catalyses the synthesis of a short RNA primer (which is about 10 nucleotides in length) complementary to the template DNA strand.

The second step is Elongation:

Once the RNA polymerase has synthesized the initial RNA primer, it proceeds to elongate the RNA chain, The RNA polymerase adds ribonucleotide complementary to the template DNA strand. This process is known as RNA chain Elongation.

After this, we have nucleosome remodelling where the DNA in eukaryotic cells is wrapped around histone proteins to form nucleosomes. As transcription proceeds, nucleosomes are temporarily disrupted and then reassembled, allowing RNA polymerase to access the DNA template.

The third step is Termination:

Eukaryotic mRNA molecules undergo post-transcriptional modification, this includes polyadenylation which involves the addition of a poly-A tail to the 3’ end of the RNA. Polyadenylation is then accompanied by cleavage of the RNA precursor at the specific site.

During this process transcription termination signals are recognized by RNA polymerase 2, leading to its dissociation from the DNA template. The termination signal will most likely include the poly-A signal.

The fourth step being RNA processing:

The first step of RNA processing is known as “capping”. Capping the 5’ end of the newly synthesized mRNA is modified with a 7-methylguanosine cap, the whole point of this cap is just to protect the mRNA as it leaves the nucleus and helps in the transportation process.

The second step is splicing, Eukaryotic genes often contain introns (which are kind of gaps or non-coding regions) and exons (which are the important bits, coding regions). In a process called splicing the annoying useless introns are cut and the exons are then pinched together with each other. This is all catalysed by a complex of RNA and proteins known as spliceosomes.

The fifth step being transport and translation:

This is when mRNA is transported out of the nucleus to the cytoplasm where it serves as a template for translation.

The sixth step is regulation:

Gene expression if tightly regulated at the transcriptional level by various elements, including transcriptional factors and chromatin modification, there is also enhancers and silencers that help regulate elements that influence transcription.

We also have post-transcriptional regulation, which is processes such as alternative splicing and RNA stability which play roles in determining the final mRNA products.

It is important to acknowledge that Eukaryotic transcription is more complex than prokaryotic transcription due to the presence of introns, the involvement of multiple RNA polymerases, and the necessity for additional processing steps.

This diagram helps visualise the main steps more simply.

Hope this was clear excuse any mistakes in grammar :)

Referencing:

Picture link above^

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GENETICS

Going to be using this account as a bank for genetics knowledge to help myself and others learn more about what makes us tick.

my first blog created in a week time will be on RNA, introns and recombinant DNA, genomics, transcriptomics, proteomics and PCR.

will be over a few posts of course. more people must hear about genetics, it is the gateway to utopia.