process of transcription in eukaryotes
Transcription is the process in which DNA is used as a template to create RNA. Here is an overview of the process of transcription in eukaryotes:
1. Initiation: Transcription begins with the assembly of the transcription initiation complex. This complex includes the RNA polymerase enzyme, as well as other proteins that help to open up the DNA helix and position the enzyme at the start of the gene to be transcribed.
2. Elongation: After initiation, RNA polymerase moves along the DNA template strand, unwinding the double helix ahead of it and synthesizing a new RNA molecule in the complementary base sequence to the DNA strand. As RNA polymerase moves along, the DNA helix is rewound behind it.
3. Termination: Transcription ends when RNA polymerase reaches the end of the gene or a termination signal in the DNA sequence. After transcription is complete, the RNA molecule is released from the DNA template and is further processed to form a mature RNA molecule.
4. Post-transcriptional modifications: The RNA molecule undergoes a series of modifications, such as the removal of introns (non-coding regions), splicing together of exons (coding regions), 5' capping, and 3' polyadenylation, before it is ready for translation into proteins.
This process is known as gene expression which is the process by which genetic information is used to synthesize RNA and proteins. Gene expression is a complex, tightly regulated process that is essential for the proper development and function of all living organisms.
The process of transcription in eukaryotes involves several steps. Here is a step-by-step breakdown of transcription in eukaryotic cells:
1. Initiation: Transcription begins when RNA polymerase II (RNAP II) binds to the promoter region of a gene. Transcription factors, which are proteins that regulate gene expression, bind to specific sequences in the promoter region and recruit RNAP II to that site.
2. DNA unwinding: The DNA double helix near the promoter region is unwound by RNAP II, forming a small open complex. This allows the template strand of DNA to be accessible for RNA synthesis.
3. Elongation: RNAP II starts moving along the template DNA strand, synthesizing a complementary RNA molecule. The enzyme adds RNA nucleotides (adenine, cytosine, guanine, and uracil) one by one, following the base-pairing rules (uracil pairs with adenine, guanine pairs with cytosine).
4. RNA processing: The initial RNA transcript, called pre-mRNA, undergoes several modifications. These include the addition of a methylated cap to the 5' end, the addition of a poly-A tail to the 3' end, and the removal of non-coding regions called introns through a process called splicing. The remaining coding regions, called exons, are then joined together.
5. Termination: Transcription terminates when RNAP II reaches a specific termination sequence on the DNA template. This causes the RNA polymerase complex to detach from the DNA, along with the newly synthesized RNA molecule. The RNA molecule is then released into the nucleus.
6. mRNA export: The mature mRNA molecule moves out of the nucleus through nuclear pores and enters the cytoplasm. Here, it can undergo translation to synthesize proteins.
It's important to note that the process of transcription in eukaryotes is more complex than in prokaryotes due to the presence of introns and the need for additional processing steps.