HMG Week 10: Transcription and Gene Expression

Vocabulary flashcards covering the process of transcription, gene structure, RNA polymerase types, and mRNA processing in prokaryotes and eukaryotes.

Gene Expression

The process by which information encoded in DNA is used to produce a functional product, usually a protein.

Central Dogma

The flow of genetic information from DNA to RNA to protein, a concept proposed by Francis Crick in 1956.

Transcription

The synthesis of an RNA molecule using a DNA template.

RNA Polymerase

An enzyme that binds to DNA, opens the double helix, and synthesizes RNA using one DNA strand as a template.

mRNA (Messenger RNA)

A type of RNA that carries genetic information from DNA to ribosomes to serve as a template for protein synthesis.

tRNA (Transfer RNA)

A type of RNA that carries amino acids during translation and contains anticodons.

rRNA (Ribosomal RNA)

A type of RNA that serves as a structural and catalytic component of ribosomes.

snRNA (Small Nuclear RNA)

A type of RNA involved in RNA processing and splicing that forms part of the spliceosome.

Initiation

The first stage of transcription where RNA polymerase binds to DNA and begins RNA synthesis.

Elongation

The second stage of transcription where RNA polymerase moves along the DNA, adding complementary RNA nucleotides.

Termination

The final stage of transcription where RNA synthesis ends and the RNA polymerase enzyme detaches from the DNA.

Promoter

A DNA sequence that serves as the binding site for RNA polymerase and determines the starting point of transcription.

RNA-Coding Region

The specific DNA sequence that is transcribed into an RNA molecule.

Terminator

A DNA sequence that signals the end of transcription.

RNA Polymerase Holoenzyme

A complex consisting of the core enzyme and the sigma ($\sigma$) factor, required for initiation in prokaryotes.

Sigma ($\sigma$) Factor

A protein responsible for recognizing promoters and positioning RNA polymerase correctly on the DNA.

-35 Region

A prokaryotic promoter consensus sequence located upstream from the transcription start site, with the sequence $5'-TTGACA-3'$.

-10 Region (Pribnow Box)

A prokaryotic promoter consensus sequence ($5'-TATAAT-3'$) where DNA unwinding begins.

Closed Complex

A state where the RNA polymerase holoenzyme is loosely bound to the -35 region and the DNA remains double-stranded.

Open Complex

A state where RNA polymerase binds tightly to the -10 region and unwinds approximately 17 base pairs of DNA to form a transcription bubble.

Promoter Clearance

The process where the sigma factor dissociates from the core enzyme after approximately 8–9 nucleotides have been synthesized.

Transcription Direction

RNA is synthesized in the $5' \rightarrow 3'$ direction, while the DNA template is read in the $3' \rightarrow 5'$ direction.

Sigma 70 ($\sigma^{70}$)

The major and most abundant sigma factor in E. coli, responsible for transcribing housekeeping genes during normal growth.

RNA Polymerase I

A eukaryotic enzyme that produces most ribosomal RNA (rRNA).

RNA Polymerase II

A eukaryotic enzyme that produces messenger RNA (mRNA) and some small nuclear RNA (snRNA).

RNA Polymerase III

A eukaryotic enzyme that produces transfer RNA (tRNA) and 5S ribosomal RNA (rRNA).

7-methylguanosine cap (m7G cap)

A modified guanine nucleotide added to the 5' end of pre-mRNA to protect against degradation and assist in ribosome recognition.

Poly-A Tail

A sequence of 50–250 adenine nucleotides added to the 3' end of pre-mRNA to improve stability and translation efficiency.

Exons

The coding sequences of a eukaryotic gene that are joined together after the removal of introns.

Introns

Non-coding sequences of a eukaryotic gene that are removed during the RNA splicing process.

Alternative Splicing

The process of joining different combinations of exons, allowing one gene to produce multiple different proteins.

Spliceosome

A complex formed by the combination of snRNAs and proteins (snRNPs) that recognizes intron boundaries, removes introns, and joins exons.