How does the RNA polymerase know where to stop copying the gene?

How does the polymerase know where to stop? A sequence of nucleotides called the terminator is the signal to the RNA polymerase to stop transcription and dissociate from the template.

How does RNA transcription stop?

During this process, an adenine (A) in the DNA binds to an uracil (U) in the RNA. 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.

How does RNA pol II stop?

When RNA polymerase II (Pol II) reaches the gene end, it first slows down over the terminator. Pol II continues to transcribe its DNA template after mRNA release. However, this is short-lived, as an exonuclease (Xrn2) degrades the transcript from its 5′ end.

How does RNA polymerase know where the promoter is?

RNA polymerases (or associated general transcription factors) are hypothesized to reach promoter sequences by facilitated diffusion (FD). In FD, a protein first binds to nontarget DNA and then reaches the target by a 1D sliding search.

How does RNA know where to go?

Thanks to TFIIB, the RNA polymerase is almost where it needs to be to start reading the gene. So it begins scanning the DNA, looking for the exact right spot to begin. To find this spot, the RNA polymerase is searching for a certain combination of DNA bases (a “motif”) that marks the beginning of genes.

Where does translation stop?

Translation ends in a process called termination. Termination happens when a stop codon in the mRNA (UAA, UAG, or UGA) enters the A site. Stop codons are recognized by proteins called release factors, which fit neatly into the P site (though they aren’t tRNAs).

Where does splicing occur?

Splicing occurs in the nucleus before the RNA migrates to the cytoplasm. Once splicing is complete, the mature mRNA (containing uninterrupted coding information), is transported to the cytoplasm where ribosomes translate the mRNA into protein. The pre-mRNA transcript contains both introns and exons.

How do eukaryotic ribosomes know to initiate translation?

This base-pairing interaction enables bacterial ribosomes to initiate translation not only at the 5´ end of an mRNA but also at the internal initiation sites of polycistronic messages. In contrast, ribosomes recognize most eukaryotic mRNAs by binding to the 7-methylguanosine cap at their 5´ terminus (see Figure 6.39).

How does RNA polymerase know where to start transcribing what is this place called?

To begin transcribing a gene, RNA polymerase binds to the DNA of the gene at a region called the promoter. Basically, the promoter tells the polymerase where to “sit down” on the DNA and begin transcribing.