Gene Expression and Transcription Overview

Study Notes

Identify the components of a gene
Describe the transcription process in terms of genetic information flow
Identify transcription proteins and consensus sequences, along with their functions
Give examples of current RNA synthesis inhibitors

A chromosome contains hundreds or thousands of genes, but only a portion is active at any given time
Different cells express distinct gene selections depending on their roles within an organism
Gene expression varies throughout developmental stages

Eukaryotic genes are made up of coding exons, noncoding introns, and noncoding consensus sequences
Noncoding regions preceding the first exon are upstream sequences; those after the last exon are downstream sequences

DNA recognition sites often bound by proteins (transcription factors) and other regulatory proteins
Promoters are DNA sequences determining the start of RNA synthesis

Regulate gene expression; can enhance or repress expression in response to signals (like hormones and chemicals)
Typically located upstream or downstream of a transcription start site

Binds to the TATA box in the minor DNA groove, causing a bend in the DNA helix.
TFIIF has DNA helicase activity, helping unwind DNA near the transcription start site
Allows RNA Polymerase to access the DNA

Alpha-amanitin (α-AMA): toxin found in Amanita phalloides mushrooms; inhibits RNA polymerase II, leading to protein deficiency and cell death
Actinomycin D: chemotherapeutic drug treating various cancers (e.g., Wilms tumor); interferes with transcription by binding to DNA during initiation, preventing RNA chain elongation
Rifampin: antibiotic inhibiting bacterial RNA synthesis by binding to bacterial RNA polymerase. This prevents the initiation by uninhibited enzymes.

Retroviruses have an RNA genome
Reverse transcriptase copies the RNA into cDNA
The cDNA is integrated into the host cell's genome for replication within the host cell.