Transcription Elongation Process Quiz

Gene expression involves two main stages: Transcription and Translation

Transcription is the process of creating an RNA copy of a gene

Transcription in eukaryotic cells consists of synthesizing RNA molecules (mRNA, rRNA, tRNA), RNA processing and modifications

Transcription requires RNA polymerases, which were first discovered in E. coli

RNA polymerase is an enzyme that catalyzes the synthesis of RNA from DNA using ribonucleoside triphosphates

RNA polymerase is composed of multiple subunits, with the sigma (σ) subunit recognizing promoter sequences on DNA

Promoters are special DNA sequences found upstream of the transcription start site (+1) in genes, and were first discovered in E. coli

The initiation of transcription begins with the binding of the sigma subunit of RNA polymerase to the promoter, followed by unwinding and opening of the DNA double helix to form a single-stranded template for RNA synthesis.

During mRNA synthesis elongation, RNA polymerase unwinds DNA ahead and rewinds behind, maintaining an unwound region of about 15 base pairs.

The internal channel between the β and β' subunits of RNA polymerase has a size of 20 base pairs and forms the active site.

Elongation of the chain and RNA transcript occur during mRNA synthesis.

Termination of transcription in E. Coli is signaled by a GC rich inverted repeat followed by 7 adenine nucleotides, which form a stable stem-loop structure, causing the RNA to separate from the DNA template.

Bacteria have one RNA polymerase responsible for transcribing all RNA genes, while eukaryotic cells contain three distinct RNA polymerases (Pol I, Pol II, Pol III) that transcribe different RNA types.

Eukaryotic RNA polymerases require a set of proteins called transcription factors and interact with chromatin to initiate transcription.

Eukaryotic transcription involves three types of RNA polymerases: RNA Polymerase I, II, and III. RNA Polymerase I synthesizes 5.8S, 18S, and 28S rRNAs, while RNA Polymerase II synthesizes mRNAs and some snRNAs, and RNA Polymerase III synthesizes tRNA genes, 5S rRNA genes, and some snRNAs.

Eukaryotic RNA polymerases recognize promoter sequences using specific proteins called transcription factors, including TF-I, TF-II, and TF-III.

Eukaryotic genes consist of a regulatory region, promoter region, initiation signals, exons, introns, and termination signals.

Initiation of mRNA transcription starts with the recognition of promoter regions by RNA Polymerase II and transcription factors.

Five general transcription factors (TF II A, TF II B, TF II D, TF II E, TF II F, and TF II H) are required for the initiation of transcription.

TF II H, a multi-subunit factor, unwinds DNA around the initiation site and phosphorylates the repeated sequences in the C-terminus (CTD) region of RNA Polymerase II, releasing it from the initiation complex.

The phosphorylated CTD forms binding sites for elongation and processing factors.

The carboxyl terminus (CTD) of RNA Polymerase II consists of tandem repeats of 7 amino acids (52 repeats) and is phosphorylated during initiation and elongation of mRNA transcription.