Transcriptional Regulation in Prokaryotes

Flashcards covering key vocabulary and concepts from the lecture notes, focusing on transcriptional regulation, gene expression, and the Lac operon.

RNA Polymerase (RNAP)

The enzyme responsible for transcription.

Promoter Sequences

DNA sequences that define where transcription of a gene by RNA polymerase begins, typically located directly upstream or at the 5' end of the transcription initiation site.

Template Strand

The DNA strand that mRNA is built from, also called the antisense strand.

Coding Strand

Corresponds to the mRNA sequence. The only difference between the coding strand and the new mRNA strand is instead of thymine, uracil takes its place in the mRNA strand.

Cis-acting DNA sequence in transcription

Promoter

Trans-acting factors

RNA polymerase and transcription factors.

-35 motif

TTGACA. Located at -35 motif

-10 motif

TATAATGGG. Located at -10 motif

Transcription

Has four basic stages: Initiation, Elongation, Termination.

Core promoter

DNA elements found at the 5’ of a gene close to the transcription start site.

TATA Box

TATAAA

Transcription elements

RNA polymerase, along with other factors.

Class I Eukaryotic genes

transcribe majority of ribosomal RNA (5.8S rRNA, 18S rRNA, 28S rRNA)

Class III Eukaryotic genes

Transcribe majority of tRNA (tRNA, 5S rRNA)

Class II Eukaryotic genes

Transcribe majority of protein coding genes (mRNA, snRNA)

Bacterial Genomes

No Nucleus. 1 single, haploid, circular chromosome, located in the “Nucleoid”. Have plasmids. Genes are organised in operons.

Eukaryotic Genomes

Have a nucleus and multiple linear chromosomes with different ploidy. Have complex gene expression. Their DNA is packaged into chromatin.

Activators

Regulatory Proteins bind DNA at or near the promoters of genes. Stimulate RNA Polymerase binding.

Repressors

Regulatory Proteins bind DNA at or near the promoters of genes. Prevent RNA Polymerase binding

Ligands

Low-molecular-weight compounds, whereby their concentration changes with environmental changes. They can bind regulatory proteins, changing their conformation