L11- Gene Expression & Mutations

Gene expression

The process of using a gene's instructions to make a protein

Transcription

Copying a gene's DNA sequence into messenger RNA

Translation

Reading an mRNA sequence to build a protein

Central dogma

The idea that information flows from DNA to RNA to protein

RNA polymerase

The enzyme that builds an RNA strand by reading a DNA template

Promoter

The DNA sequence where RNA polymerase attaches to start transcription

TATA box

A short DNA sequence in many eukaryotic promoters that helps position RNA polymerase

Transcription factor

A protein that helps RNA polymerase find and bind to the promoter

Transcriptional start site (TSS)

The exact spot where RNA copying begins

Initiation

The first stage of transcription, when RNA polymerase binds the promoter and unwinds the DNA

Elongation

The stage of transcription or translation when the new strand or protein chain is actively being built

Termination

The final stage of transcription or translation, when the process stops and the molecules are released

Primary transcript (pre-mRNA)

The first, unedited copy of RNA made directly from DNA

5' cap

A special modified nucleotide added to the front of pre-mRNA

Poly-A tail

A long chain of adenine nucleotides added to the end of pre-mRNA

Exon

A piece of a gene that codes for protein and stays in the final mRNA

Intron

A piece of a gene that does not code for protein and gets cut out

Splicing

Cutting introns out of pre-mRNA and joining the exons together

Spliceosome

The molecular machine made of protein and snRNA that performs splicing

Alternative splicing

Mixing and matching exons in different ways to make different proteins from one gene

Messenger RNA (mRNA)

The RNA copy of a gene that carries instructions to the ribosome

Ribosomal RNA (rRNA)

RNA that forms part of the ribosome's structure

Ribozyme

An RNA molecule that can act as a catalyst

Transfer RNA (tRNA)

RNA that carries a specific amino acid to the ribosome during translation

Small nuclear RNA (snRNA)

RNA that helps the spliceosome cut out introns

Polycistronic

An mRNA that carries instructions for more than one protein, common in prokaryotes

Monocistronic

An mRNA that carries instructions for just one protein, common in eukaryotes

Genetic code

The set of rules that matches each three-letter codon to an amino acid

Codon

A group of three mRNA bases that codes for one amino acid

Reading frame

The way codons are grouped in sets of three starting from a fixed point

Start codon

The codon (AUG) that marks where translation begins

Stop codon

A codon that signals translation to stop

Redundant code

The fact that most amino acids are coded for by more than one codon

Anticodon

The three-base sequence on a tRNA that pairs with a codon on mRNA

Aminoacyl-tRNA synthetase

The enzyme that attaches the correct amino acid to its matching tRNA

Peptide bond

The bond that links amino acids together in a protein chain

Release factor

A protein that ends translation when a stop codon is reached

Polyribosome

A string of several ribosomes translating the same mRNA at once

Point mutation

A change at just one base pair in DNA

Silent mutation

A point mutation that does not change the amino acid produced

Missense mutation

A point mutation that changes one amino acid in the protein

Nonsense mutation

A point mutation that creates an early stop codon, cutting the protein short

Frameshift mutation

An insertion or deletion that shifts the reading frame, scrambling everything after it

Indel

An insertion or deletion of DNA bases

Chromosomal mutation

A change affecting a large segment of a chromosome

Insertion

Adding extra DNA bases into a sequence

Deletion

Removing DNA bases from a sequence

Duplication

Copying a segment of DNA an extra time

Inversion

Flipping a segment of DNA backward

Translocation

Moving a piece of DNA to a different chromosome

Spontaneous mutation

A mutation that happens naturally, without an outside cause, like a DNA polymerase error

Induced mutation

A mutation caused by an outside factor, like chemicals or radiation

Thymine dimer

A kink in DNA caused when UV light bonds two thymine bases together incorrectly