Transcription is the process by which the genetic information stored in DNA is copied into RNA. This process is essential for the expression of genes and the synthesis of proteins. Transcription occurs differently in eukaryotes and prokaryotes due to differences in the organization of their genetic material.
Transcription in Prokaryotes
Initiation: The first step in prokaryotic transcription is initiation, which is initiated by a protein called RNA polymerase. RNA polymerase binds to a specific site on the DNA called the promoter region, which signals the start of a gene.
Elongation: The next step is elongation, during which RNA polymerase unwinds the DNA double helix and adds nucleotides to the growing RNA chain. The RNA polymerase moves along the DNA template strand, synthesizing RNA in the 5′ to 3′ direction.
Termination: The final step in prokaryotic transcription is termination, which occurs when RNA polymerase reaches a specific sequence of nucleotides called the terminator region. The RNA polymerase dissociates from the DNA template and releases the newly synthesized RNA transcript.
Transcription in Eukaryotes
Initiation: Eukaryotic transcription is more complex than prokaryotic transcription, as eukaryotic DNA is organized into chromatin and contains multiple types of RNA polymerases. RNA polymerase II is responsible for transcribing protein-coding genes. Initiation of transcription in eukaryotes involves several steps. First, specific DNA-binding proteins called transcription factors bind to the promoter region of the gene. These transcription factors recruit RNA polymerase II to the promoter region, which initiates transcription.
Elongation: Once RNA polymerase II is recruited to the promoter region, it unwinds the DNA double helix and begins synthesizing RNA in the 5′ to 3′ direction. However, unlike prokaryotic transcription, elongation in eukaryotes is slower and more complex. RNA polymerase II must navigate through chromatin, which is tightly packed and can inhibit transcription. A number of additional factors are involved in elongation, including elongation factors and RNA processing proteins.
Termination: The final step in eukaryotic transcription is termination. Unlike prokaryotes, eukaryotic genes can have multiple polyadenylation sites, which result in the production of multiple mRNA transcripts from a single gene. Once transcription is complete, the mRNA transcript undergoes further processing, including splicing and the addition of a poly(A) tail.
Overall, transcription in both prokaryotes and eukaryotes is a complex process that involves multiple steps and factors. However, the differences in the organization of genetic material in prokaryotes and eukaryotes result in some key differences in the transcription process.
⦿ Transcription is the process by which genetic information stored in DNA is copied into RNA, which is essential for the expression of genes and the synthesis of proteins.
⦿ In prokaryotes, transcription involves initiation, elongation, and termination. RNA polymerase binds to the promoter region, unwinds the DNA double helix, and adds nucleotides to the growing RNA chain. Termination occurs when RNA polymerase reaches the terminator region.
⦿ In eukaryotes, transcription is more complex and involves multiple types of RNA polymerases. Initiation involves the binding of transcription factors to the promoter region and recruitment of RNA polymerase II. Elongation involves slow and complex movement of RNA polymerase II through chromatin. Termination involves multiple polyadenylation sites and further processing of the mRNA transcript.
⦿ Transcription can be regulated by various factors, including transcription factors, epigenetic modifications, and non-coding RNAs.
⦿ Errors during transcription can lead to mutations and disease, highlighting the importance of accurate transcription in maintaining genome integrity.
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Published: 05/03/2023, 1456
Graduated from the University of Kerala with B.Sc. Botany and Biotechnology. Attained Post-Graduation in Biotechnology from the Kerala University of Fisheries and Ocean Science (KUFOS) with the third rank. Conducted various seminars and attended major Science conferences. Done 6 months of internship in ICMR – National Institute of Nutrition, Hyderabad. 5 years of tutoring experience.
