AP Biology UNIT 6- gene expression

Gene expression

The process by which information in a gene is used to produce a functional product such as a protein or RNA

Central dogma

The flow of genetic information from DNA to RNA to protein

Transcription

The synthesis of RNA from a DNA template

Translation

The synthesis of a polypeptide using the information in mRNA

RNA polymerase

Enzyme that synthesizes RNA by adding complementary RNA nucleotides during transcription

Promoter

Region of DNA where RNA polymerase binds to begin transcription

Terminator

DNA sequence that signals the end of transcription

Template strand

The DNA strand used by RNA polymerase to synthesize RNA

Coding strand

DNA strand with the same sequence as mRNA except T replaces U

mRNA

Messenger RNA that carries genetic information from DNA to ribosomes

tRNA

Transfer RNA that brings amino acids to the ribosome during translation

rRNA

Ribosomal RNA that makes up ribosomes

Codon

A three-nucleotide sequence on mRNA that codes for an amino acid

Anticodon

Three-nucleotide sequence on tRNA complementary to an mRNA codon

Ribosome

Structure composed of rRNA and proteins where translation occurs

Start codon

AUG, signals the beginning of translation and codes for methionine

Stop codon

UAA, UAG, or UGA, signals the end of translation

Reading frame

The grouping of nucleotides into codons during translation

Polypeptide

Chain of amino acids formed during translation

Peptide bond

Bond that links amino acids together in a polypeptide

Pre-mRNA

Initial RNA transcript that contains introns and exons

Introns

Noncoding regions of RNA that are removed during RNA processing

Exons

Coding regions of RNA that are spliced together

RNA splicing

Process that removes introns and joins exons

Spliceosome

Complex of proteins and RNA that carries out RNA splicing

5′ cap

Modified guanine nucleotide added to mRNA that protects it and aids ribosome binding

Poly-A tail

Chain of adenine nucleotides added to mRNA that increases stability

Gene regulation

The control of gene expression

Differential gene expression

Expression of different genes in different cell types

Operon

A cluster of genes under the control of a single promoter (prokaryotes)

Operator

DNA segment in an operon where a repressor binds

Repressor

Protein that blocks transcription when bound to DNA

Inducible operon

Operon usually turned off but activated when an inducer is present

Repressible operon

Operon usually turned on but inhibited when a corepressor is present

Lac operon

Inducible operon controlling lactose metabolism in E. coli

Trp operon

Repressible operon controlling tryptophan synthesis

Transcription factors

Proteins that help regulate transcription in eukaryotes

Enhancers

DNA sequences that increase transcription when bound by activators

Silencers

DNA sequences that decrease transcription when bound by repressors

Activators

Proteins that increase transcription by binding enhancers

Epigenetics

Heritable changes in gene expression that do not involve changes to DNA sequence

DNA methylation

Addition of methyl groups to DNA that reduces gene expression

Histone acetylation

Addition of acetyl groups to histones that increases gene expression

Chromatin remodeling

Changes in chromatin structure that affect gene expression

Post-transcriptional regulation

Control of gene expression after transcription

Alternative splicing

Different combinations of exons produce different proteins

mRNA degradation

Breakdown of mRNA to regulate protein production

RNA interference (RNAi)

Process where small RNAs inhibit gene expression

miRNA

Small RNA that binds mRNA and blocks translation

siRNA

Small RNA that leads to degradation of target mRNA

Mutation

A change in the nucleotide sequence of DNA

Point mutation

Mutation affecting a single nucleotide

Silent mutation

Mutation that does not change the amino acid sequence

Missense mutation

Mutation that changes one amino acid

Nonsense mutation

Mutation that creates a premature stop codon

Frameshift mutation

Mutation caused by insertion or deletion that alters the reading frame