What is Transcription?
- Transcription is the process by which the genetic information stored on DNA strands is transferred into an RNA-RNA strand via the polymerization process caused by enzymes known as DNA-dependent polymerases.
- This is the very first stage of gene expression in which the information is transferred between structures to the next.
- In the process of transcription, molecules of RNA get activated, stretched and then terminated. The RNA produced is non-genetic RNA.
- Transcription is an essential step for translation. It happens in the event of a requirement for a specific gene at a particular time to the specific tissue.
- One strand of DNA known as the template strand, gets replicated during transcription. that resulting RNA strands form mono-stranded messenger-RNA (mRNA).
- The transcription of a particular gene occurs close to the chromosomal location of the gene. This is generally a narrow section of the chromosome.
- The entire process of transcription is highly controlled which is controlled and catalyzed by enzyme DNA-dependent RNA polymerase.
- The first step is the identification of DNA sequences, also known as promoter sequences, which signify the start for the genetic code.
- The process is followed by the division of two DNA strands and the replication of one the DNA strands using the polymerase RNA.
- The RNA polymerase that is found in Eukaryotes is different and more complicated as compared to prokaryotes.
- The sequence that is created after replication is a complement to that of the original template since it follows the complementary bases pairing guidelines of DNA with the exception that thymine is replaced by uracil.
- In prokaryotes, the entire process is controlled by proteins that act as signaling or operators. They end it by blocking RNA polymerase after the process is completed.
- In eukaryotes, the various proteins referred to as transcription factors play a role in the control of transcription.
- Additionally, the post-transcriptional alteration is also seen in eukaryotes in which the pre-mRNA (the product that transcription) is altered through the process of splicing, which occurs before the mature mRNA gets to the ribosomes that are used for translation.
- The mRNA produced functions as a guideline for protein production in transcription.
- The sequence of DNA selected to be used for transcription, rRNA as well as tRNA synthesis can also take place.
- The transcription process takes place inside the nucleus of the eukaryotes as well as in the in the cytoplasm of prokaryotes where the enzymes as well as transcriptional factors are present.
- It is blocked by certain antibiotics such as rifampicin and 8Hydroxyquinoline.
- The process is detected with methods such as DNA microarrays, RTPCR hybridization in situ, and northern Blotting.
What is Translation?
- The process of translation is of protein synthesis, where the RNA information is expressed as polypeptide chains.
- It is the second and final step in the process of expression of genes where the information encoded by the mRNA sequence is converted into the amino acid sequence.
- The beginning point for translation lies in the messenger RNA that has formed through the process of transcription of a specific DNA sequence. Translation follows transcription.
- Although the information contained in the mRNA is used to create amino acid sequences other types of RNA, such as tRNA are also needed for the procedure.
- Similar to transcription, translation can also be controlled by a variety of elements and enzymes. The most crucial enzyme is aminoacetyl synthetase for tRNA.
- The process begins with the initial phase, which involves binding of mRNA to Ribosomes. Then comes the transfer and attachment of activated amino acid on the transcriptase.
- The next process is elongation. the two amino acids get linked by the peptide bond, as molecules mRNA and ribosomes shift in relation each other to enable the simultaneous translation of codons.
- After all codons have been translated, the resulting polypeptide sequence is separated from the complex of translation and ribosomes are released to start a new phase of translation.
- The termination is followed by post-translational modification where the polypeptide must be folded in order to get the three-dimensional shape. This happens in the endoplasmic-reticulum and Golgi apparatus in the cell. Consequently the polypeptide chains are transferred to these organelles.
- Some modifications may be chemical and require the attaching functional group to sequence of peptides.
- The process of translating is controlled by the binding of ribosomal subunits with this translation component. Ribosomes are enzymes that regulate different actions.
- In eukaryotes it is located in the ribosomes that are associated with the endoplasmic-reticulum, whereas in prokaryotes it is located within the cytoplasm.
- The translation is blocked by antibiotics such as tetracycline streptomycin and chloramphenicol anisomycin, Cycloheximide, and so on.
- The procedure of translating can also be identified using methods like western blotting, immunoblotting enzyme assays Protein sequencing, and so on.
Differences between Transcription and Translation
In prokaryotes, both transcription as well as translation are carried out within the cytoplasm, due to the absence of a nucleus. In eukaryote transcription is carried out within the nucleus, while translation takes place in ribosomes that are located on the rough endoplasmic layer in the cytoplasm.
Transcription occurs through RNA polymerase , as well as the other proteins, which are referred to by the term transcription factor. It is inducible such as in the spatio-temporal regulation of development genes, or consitutive as is seen in the case of housekeeping genes such as Gapdh.
Translation is carried out by the ribosome, a multisubunit structure composed of rRNA and proteins.
Transcription starts with RNA Polymerase attaching to the promoter area of the DNA. A combination of transcription factor and binding the promoter form the transcription initiation complex. The promoter is composed of a core area similar to the TATA box, where the complex is bound. It is at this point that RNA polymerase unravels the DNA.
The process of translation begins with the creation of the initiation complex. The subunit ribosome, the three factors that initiate the process (IF1, the IF2 and the IF3) and methionine carrying tRNA are bound to the mRNA close to the AUG start codon.
During transcription, the RNA polymerase following the first failed attempts, traverses the template’s strand of DNA in a 3 5′ and ” directions and produces a second DNA strand of RNA in 5′-3 directions. When the RNA polymerase advances, the DNA strand which has been transcriptionally transcribed, it is rewinded to create an oblique the helix.
During translation, the incoming aminoacyl tRNA binds on the codon (sequences of three nucleotides) at the A-site. Then a protein bond forms between the newly formed amino acid, and expanding chain. The peptide moves to the next codon to prepare to receive the amino acid. The process continues in the 5′-3 direction.
The termination of transcription in prokaryotes could be Rho-independent where the formation of a GC hairpin loop with a high amount of hairpins forms or it can be Rho-dependent where a protein molecule Rho disrupts the DNA-RNA interplay. In eukaryotes when an end-of-life sequence is encountered the RNA nascent transcript gets released and is poly-adenylated.
When the ribosome comes into contact with one of the stop codons, it detaches the ribosome before releasing the polypeptide.
The final outcome of transcription can be an RNA transcription, which could be one of the following types of RNA: mRNA TRNA, rRNA and other Non-coding RNA (like microRNA). In prokaryotes, the MRNA produced is polycistronic, and for eukaryotes they are monocistronic.
The final product of translation is a chain of polypeptides that is folded and undergoes post translational modifications to make functional proteins.
Post Process Modification
In post transcriptional modifications in eukaryotes a 5 3 poly tail is added , and introns are spliced. In prokaryotes this process is not present.
There are a variety of post-translational changes that occur , such as phosphorylation, SUMOylation and disulfide bridges’ creation and farnesylation, among others.
Transcription inhibition is caused by Rifampicin (antibacterial) as well as 8-hydroxyquinoline (antifungal).
Anisomycin inhibits translation and cycloheximide. Chloramphenicol is the most pot streptomycin and tetracyclin and puromycin.
Methods to measure and detect
For Transcription, RT-PCR DNA microarrays, In-situ Hybridization, Northern blot, RNA-Seq is frequently used to measure and detect. For translation Western blotting, immunoblotting and enzyme assay protein sequencing, Metabolic labeling, and proteomics are utilized to measure and detect.
Crick’s central dogma: DNA —> Transcription —> RNA —> Translation —> Protein
Key Differences between Transcription and Translation (Transcription vs Translation)
|Basis for Comparison||Transcription||Translation|
|Definition||Transcription is the process by which the genetic information stored on DNA strands is transferred into an RNA-RNA strand via an array of polymerization reactions caused by enzymes known as DNA-dependent polymerases.||Translation is the process of protein synthesis in which the RNA information is expressed as polypeptide chains.|
|Gene expression||Transcription is the very first step in the process of expressing genes.||The translation process is the second and final stage of expression.|
|Occurs||Transcription occurs before translation.||The Translation process begins after the transcription.|
|Precursor||The transcription precursor is the antisense or non-coding DNA Strand.||The precursor to transcription is the mRNA that results by transcription.|
|Material in raw form||The transcription raw material comprises the four bases of RNA, the adenine, guanine and uracil bases and cytosine.||The amino acids of twenty are the basic ingredients of translation.|
|Initiation||The recognition of particular DNA sequences, also known as promoter sequences, starts transcription and signals the start in the life of the gene.||Binding of the mRNA starts the translation process to the ribosomes.|
|Elongation||The lengthening of RNA sequences happens through the binding of pair of bases onto the newly formed sequence.||The lengthening of proteins occurs due to the bonding to amino acids.|
|Product||The end product that is produced by transcription mRNA-like molecule, which is a complement to DNA Strand.||The result of translation are the peptide sequences encoded by the sequence of mRNA.|
|Synthesis of||Transcription leads to the synthesizing of sequences of RNA.||Translation leads to the protein synthesis.|
|Site||The transcription process occurs in the nucleus in eukaryotes as well as in the cell cytoplasm of prokaryotes in which the regulators and enzymes are found.||The process of translation occurs in the cytoplasm of prokaryotes as well within the ribosomes that line the endoplasmic reticulum of eukaryotes.|
|Enzymes||The most important enzymes involved in transcription are DNA-dependent polymerase.||The main enzyme the one responsible for the process is aminoacetyl synthetase.|
|Regulation||Transcription is controlled by different transcriptional factors in eukaryotes as well as through operons within prokaryotes.||The control of translation is carried out by interaction of ribosomal units with the transcription complex.|
|Modifications post-event||Post-transcriptional modifications are the modification in pre-mRNA (the product of transcription) through the process of Splicing prior to the mature mRNA gets to the ribosomes to allow translation.||Post-translational modifications require the stretching of chains of polypeptides in order to create the three-dimensional structure.|
|Detection||The process is detected using techniques like DNA microarray, RT-PCR in-situ hybridization and northern Blotting.||The method of translation could be identified through methods such as western Blotting, immunoblotting enzyme assays, Protein sequencing, etc.|
|Inhibition||It is blocked by certain antibiotics such as rifampicin and 8Hydroxyquinoline.||The translation is impeded by antibiotics, such as tetracycline streptomycin and chloramphenicol anisomycin, cycloheximide and so on.|