How does RNA polymerase know which genes to transcribe?

How does RNA polymerase know which genes to transcribe?

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). The sigma subunit conveys promoter specificity to RNA polymerase; that is, it is responsible for telling RNA polymerase where to bind.

How does RNA polymerase know where to stop transcribing a gene into mRNA?

Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.

How are genes transcribed into mRNA?

During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase II catalyzes the formation of a pre-mRNA molecule, which is then processed to form mature mRNA (Figure 1).

How does a cell know which sequences to remove from the pre-mRNA transcript as introns?

How does a cell know which sequences to remove from the pre-mRNA transcript as introns? Complementary sequences in the snRNA bind to the splice sites in the primary transcript. What factors are recognized by the cell in order to recognize the stop codon and disassemble the translation machinery?

How does RNA know which strand to transcribe?

RNA polymerase binds to the promoter, which orients it on the correct strand and in the correct direction, after which it can proceed to transcribe the gene.

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 polymerase know where to start and stop?

How does the RNA polymerase know where to start and stop? Each gene has a beginning and an end. At the beginning of each gene is a similar sequence that tells the RNA polymerase to start working. The same is true at the end of each gene where a specific sequence tells the RNA polymerase to stop transcription.

How is pre-mRNA processed before leaving the nucleus?

Messenger RNA, or mRNA, leaves the nucleus through pores in the nuclear membrane. During mRNA processing, the introns (non-coding regions) of the pre-mRNA are removed, and the exons (the coding regions) are spliced together. Additionally, a 5′ cap and a 3′ poly A tail are added to the pre-mRNA.

How does RNA polymerase distinguish which DNA strand to transcribe?

RNA polymerase synthesizes an RNA strand complementary to a template DNA strand. It synthesizes the RNA strand in the 5′ to 3′ direction, while reading the template DNA strand in the 3′ to 5′ direction. The template DNA strand and RNA strand are antiparallel.

How does RNA polymerase bind to DNA and begin transcription?

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. The promoter region comes before (and slightly overlaps with) the transcribed region whose transcription it specifies.

How does RNA know which strand of DNA to copy?

RNA knows which strand to copy because it finds the sequence of code that says “Here’s a gene to read”, termed a promoter, which causes an RNA polymerase to bind to the strand and transcribe the code in the 3′ to 5′ direction, creating mRNA, until it reaches a sequence that tells the polymerase to stop.

Why does RNA polymerase excise many correct bases?

However, RNA polymerase also excises many correct bases as part of the cost for improved accuracy. The majority of genes carried in a cell’s DNA specify the amino acid sequence of proteins; the RNA molecules that are copied from these genes (which ultimately direct the synthesis of proteins) are called messenger RNA (mRNA) molecules.

What does RNA know about a gene?

RNA doesn’t know anything. Genes occur on both strands of DNA in a chromosome. Transcription of DNA into RNA occurs when RNA polymerase, the enzyme that makes RNA, is recruited to the region just upstream of the beginning of a gene.