Prokaryotic Transcription and RNA Modification Vocabulary

Flashcards covering vocabulary terms related to transcription and RNA modification.

Transcription

The act or process of making a copy of a DNA sequence into an RNA sequence.

Protein-coding genes (structural genes)

Genes that code for the amino acid sequence of a polypeptide.

Messenger RNA (mRNA)

RNA that carries the base sequence that determines the amino acid sequence of a polypeptide during translation.

DNA replication

Makes DNA copies that are transmitted from cell to cell and from parent to offspring.

Chromosomal DNA

Stores information in units called genes.

Transcription

Produces an RNA copy of a gene.

Messenger RNA

A temporary copy of a gene that contains information to make a polypeptide.

Translation

Produces a polypeptide using the information in mRNA.

Polypeptide

Becomes part of a functional protein that contributes to an organism’s traits.

Promoters

DNA base sequences that define the beginning and end of a gene and regulate the level of RNA synthesis.

Gene expression

The overall process by which the information within a gene is used to produce a functional product.

Regulatory elements

Site for the binding of regulatory transcription factor proteins to influence the rate of transcription.

Promoter

Site for RNA polymerase binding; signals the beginning of transcription.

Terminator

Signals the end of transcription.

Ribosome-binding site

Site for ribosome binding to mRNA in bacteria; translation begins near this site in the mRNA.

Codons

3 nucleotide sequences within the mRNA that specify particular amino acids.

Start codon

Specifies the first amino acid in a polypeptide sequence.

Stop codon

Specifies the end of polypeptide synthesis.

Polycistronic mRNA

Codes two or more polypeptides (in bacteria).

Template strand

The DNA strand that is actually transcribed (used as the template).

Coding strand (sense strand / non-template strand)

The opposite strand of the template strand whose base sequence is identical to the RNA transcript, except for the substitution of uracil in RNA for thymine in DNA.

Transcription

Occurs in three stages: initiation, elongation, and termination.

Promoters

Direct the exact location for the initiation of transcription and are typically located just upstream of the transcription start site.

Consensus sequence

The most common sequence that is likely to result in a high level of transcription.

RNA polymerase

The enzyme that catalyzes the synthesis of RNA.

RNA polymerase holoenzyme

Composed of a core enzyme (α2ββ’ω subunits) and a sigma factor (σ subunit) in E. coli.

RNA polymerase holoenzyme

Binds loosely to the DNA, scans along the DNA until it encounters a promoter region, and recognizes the -35 and -10 regions.

Closed complex

Formed when RNA polymerase binds to the promoter.

Open complex

Formed when the TATAAT box in the -10 region is unwound.

Elongation phase

The core enzyme slides down the DNA to synthesize an RNA strand after the sigma factor is released.

Elongation of transcript

The open complex formed by the action of RNA polymerase is about 17 bases long. Rate of RNA synthesis is about 43 nucleotides per second.

Synthesis of RNA transcript

RNA polymerase slides along the template strand in a 3’ to 5’ direction, and RNA is synthesized in a 5’ to 3’ direction.

Termination of bacterial transcription

The end of RNA synthesis.

Rho-dependent termination

Requires a protein known as ρ (rho).

Rho-independent termination

Does not require ρ.

ρ-independent termination

Facilitated by a uracil-rich sequence at the 3’ end of the RNA and a stem-loop structure upstream of the uracil-rich sequence.