SCH2226 Human Molecular Genetics - Gene Expression: Transcription

Comprehensive vocabulary flashcards covering the central dogma, transcription processes in prokaryotes and eukaryotes, RNA polymerases, and post-transcriptional modifications based on the SCH2226 lecture notes.

Central Dogma

The flow of information from DNA to RNA to Protein, a term coined by Francis Crick in 1956.

Transcription

The process of copying genetic information in DNA into an RNA sequence, using a DNA template and the enzyme RNA polymerase.

Initiation

The first step of transcription where RNA polymerase binds to the DNA.

Elongation

The second step of transcription where RNA polymerase adds nucleotides to the growing RNA chain.

Termination

The final step of transcription where transcription stops and RNA polymerase dissociates.

Messenger RNA (mRNA)

An RNA molecule that carries genetic information from DNA for protein synthesis.

Transfer RNA (tRNA)

Small RNA molecules featuring an anticodon and an amino acid attachment site, involved in translation.

Ribosomal RNA (rRNA)

A type of RNA that combines with proteins to form ribosomes.

Small Nuclear RNA (snRNA)

RNA molecules involved in splicing primary transcripts to form mature mRNA in eukaryotes.

Sigma factor

A protein in bacterial initiation that binds to RNA polymerase to form a holoenzyme and guides it to specific promoter sequences.

Promoter

A sequence in a gene that attracts RNA polymerase to begin transcription at a specific site.

RNA-coding sequence

The specific region of a gene that is transcribed into RNA.

Terminator region

The region of a gene specifying where transcription will stop.

-35 region consensus sequence

A promoter sequence in prokaryotes typically represented as $5'-TTGACA-3'$.

-10 region consensus sequence

A promoter sequence in prokaryotes typically represented as $5'-TATAAT-3'$.

$$\sigma^{70}$$

The most abundant sigma factor in E. coli cells, used for most gene promoters.

RNA Polymerase I

A eukaryotic enzyme located in the nucleolus that transcribes the three major ribosomal RNAs: $28S$, $18S$, and $5.8S$.

RNA Polymerase II

A eukaryotic enzyme located in the nucleus that transcribes messenger RNA (mRNA) and small nuclear RNA (snRNA).

RNA Polymerase III

A eukaryotic enzyme located in the nucleus that transcribes transfer RNA (tRNA), $5S$ rRNA, and some snRNA.

TATA box

A core promoter element (also known as the Hogness box) located at $-30$ in eukaryotes with the sequence $TATAAAA$.

TFIID

A complex consisting of TATA Binding Protein (TBP) and TBP-associated factors (TAFs) that initiates eukaryotic transcription complex formation.

Enhancers

DNA sequences required for maximal transcription of a gene that can act in cis (same strand) or trans (different strand).

Introns

Intervening sequences in a primary transcript that do not code for proteins and are removed during splicing.

Spliceosome

The cellular machinery responsible for intron splicing, consisting of five small nuclear RNAs ($U1$, $U2$, $U4$, $U5$, and $U6$) and over $60$ proteins.

snRNP

A small ribonucleoprotein, often called a 'snurp', formed by snRNA and proteins to facilitate splicing.

$5'$ Capping

The addition of a $7\text{-methylguanosine}$ structure to the $5'$ end of eukaryotic mRNA for protection and translation initiation.

Poly(A) tail

A sequence of up to $200$ A residues added to the $3'$ end of mRNA by the enzyme poly(A) polymerase to protect it from exonucleases.

AAUAAA

The recognition site in eukaryotic mRNA where cleavage occurs approximately $20\text{ bp}$ upstream before the addition of a poly(A) tail.