Transcription, RNA Processing and Translation: every key term you need (+ practice quiz)
25 flashcard terms for Genetics Topic 4, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 8-question quiz — free, no account needed.
Sequence information flows from the genome to messenger molecules and then to protein, with the reverse route to protein sequence never used.
Promoter
The sequence upstream of a gene where the transcription machinery assembles. Its strength largely determines the baseline rate of transcript production.
Template strand
The strand read by the polymerase. The transcript matches the other strand in sequence, apart from the substitution of uracil for thymine.
Sigma factor
A bacterial subunit that directs the polymerase to specific promoter classes, so swapping it redirects transcription to a whole set of genes at once.
Transcription bubble
The locally unwound region where the template is read and the growing transcript is briefly paired with it before being displaced.
Intrinsic termination
Bacterial termination in which the transcript folds into a hairpin followed by a weak run of pairing, causing the polymerase to release.
Eukaryotic polymerase specialization
Different polymerases transcribe protein-coding genes, ribosomal genes and small structural transcripts, and they differ in inhibitor sensitivity.
General transcription factors
Proteins that must assemble at a eukaryotic promoter before the polymerase can bind, making transcription initiation inherently regulated.
Enhancer
A regulatory sequence that can act over long distances and in either orientation, contacting the promoter through looping of the intervening region.
Five prime cap
A modified nucleotide added to the front of a eukaryotic transcript that protects it from degradation and is required for efficient ribosome loading.
Poly-A tail
A run of adenines added after cleavage at the transcript's end, which influences stability and export and shortens with age in the cytoplasm.
Intron and exon
Introns are removed from the transcript and exons are retained and joined. The distinction is a property of the transcript, not of the sequence itself.
Spliceosome
A large complex of small nuclear particles and proteins that recognizes splice boundaries and catalyses removal of the intervening segment.
Alternative splicing
Joining different exon combinations from one transcript, so a single gene can specify several related proteins in different tissues.
Genetic code properties
The code is read in non-overlapping triplets, is redundant because most amino acids have several codons, and is nearly universal across life.
Wobble position
The third base of a codon, where pairing is relaxed, which lets one transfer molecule read several codons and buffers many third-position changes.
Transfer RNA charging
An enzyme attaches the correct amino acid to its transfer molecule, and this step, not the ribosome, is where amino acid identity is checked.
Ribosome sites
The three functional positions through which transfer molecules pass in order, holding the growing chain, accepting the next residue and releasing the spent carrier.
Initiation in bacteria
A sequence upstream of the start codon pairs with ribosomal RNA to position the ribosome, which allows several coding regions on one transcript.
Initiation in eukaryotes
The small subunit binds the capped end and scans forward to the first suitable start codon, which is why one transcript normally encodes one protein.
Elongation cycle
Repeated selection of a matching transfer molecule, peptide bond formation and movement of the ribosome by one codon, each step checked for accuracy.
Release factor
A protein that recognizes a stop codon and triggers hydrolysis of the finished chain from the final carrier.
Polysome
Several ribosomes translating one transcript at once, multiplying output without needing additional transcripts.
Signal sequence
An amino-terminal tag that directs a growing chain to the secretory pathway, after which it is usually cleaved from the mature protein.
Nonsense-mediated decay
A surveillance pathway that destroys transcripts with a premature stop codon, preventing accumulation of truncated proteins.