What is initiation elongation and termination?
Translation of an mRNA molecule by the ribosome occurs in three stages: initiation, elongation, and termination. During initiation, the small ribosomal subunit binds to the start of the mRNA sequence. Lastly, termination occurs when the ribosome reaches a stop codon (UAA, UAG, and UGA).
What is the process of elongation?
Basically, elongation is the stage when the RNA strand gets longer, thanks to the addition of new nucleotides. During elongation, RNA polymerase “walks” along one strand of DNA, known as the template strand, in the 3′ to 5′ direction.
How does initiation start?
During initiation, the small ribosomal subunit binds to the start of the mRNA sequence. Then a transfer RNA (tRNA) molecule carrying the amino acid methionine binds to what is called the start codon of the mRNA sequence. The start codon in all mRNA molecules has the sequence AUG and codes for methionine.
What are the three 3 stages of translation?
Translation of an mRNA molecule occurs in three stages: initiation, elongation, and termination.
Does termination of translation require energy?
Protein synthesis is an energy‐intensive process. High‐energy phosphate bonds are expended for each peptide bond formed. One high‐energy bond is consumed when an amino acid is activated by its aminoacyl‐tRNA synthetase.
What happens during termination of transcription?
Termination is the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA.
What is a termination sequence?
A sequence in DNA that signals termination of transcription to RNA Polymerase. This should not be confused with terminator codons that are the stopping signal for translation.
Where is the termination sequence found?
DNA sequences within the promoter or the transcription units are often referred to as elements, boxes, sites, or regions. In a prokaryotic gene, the transcription unit has a promoter on the 5′ end (upstream) of the coding strand and a termination signal on the 3′ end (Fig.
How is transcription terminated in prokaryotes?
Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly-made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals: one is protein-based and the other is RNA-based.
What causes the termination of transcription in prokaryotes?
Termination in Prokaryotes Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. The result is a stable hairpin that causes the polymerase to stall as soon as it begins to transcribe a region rich in A–T nucleotides.
What initiation and termination factors are involved in transcription in prokaryotes?
Prokaryotic Termination Signals One is protein-based and the other is RNA-based. Rho-dependent termination is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls.
What is the first step during transcription initiation in prokaryotes?
The first step in transcription is initiation, when the RNA pol binds to the DNA upstream (5′) of the gene at a specialized sequence called a promoter (Figure 2a). In bacteria, promoters are usually composed of three sequence elements, whereas in eukaryotes, there are as many as seven elements.
Which is most directly responsible for the sequence of amino acids in a protein?
The sequence of nucleotides, coded in triplets (codons) along the mRNA, that determines the sequence of amino acids in protein synthesis. The DNA sequence of a gene can be used to predict the mRNA sequence, and the genetic code can in turn be used to predict the amino acid sequence.