13 mRNA and Transcription

codon

three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the termination and release of a polypeptide chain during translation

stop codon

one of the three mRNA codons that specifies termination of translation

chromosome

a molecule of DNA; part or all of the genome. Also refers to the condensed version of chromatin that is found within cells undergoing cell division.

plasmid

extrachromosomal circular DNA molecule that may contain one or a few genes; common in prokaryotes

promoter

DNA sequence to which RNA polymerase and associated factors bind and initiate transcription

transcription bubble

region of locally unwound DNA that allows for transcription of mRNA

template strand

strand of DNA that is used to make the complementary mRNA molecule; sequence is complementary to the mRNA

nontemplate strand

strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA

operon

collection of genes involved in a pathway that are transcribed together as a single mRNA in prokaryotic cells

repressor

protein that binds to the operator of prokaryotic genes to prevent transcription

activator

protein that binds to prokaryotic operators to increase transcription

inducer

a molecule that increases gene expression, either by binding to a repressor and inactivating it, or binding to an activator and activating it

enhancer

segment of DNA that influences the transcription of a specific gene. can be upstream, downstream, perhaps thousands of nucleotides away, or on another chromosome

transcription factor

a protein that binds to DNA and regulates gene expression by promoting or suppressing transcription

Gene expression

the process of making a functional product (usually refers to a protein) from information in a gene; includes transcription and translation

Transcription

the process of making RNA from DNA

Translation

the process of making a polypeptide from the information in RNA

exon

sequence present in protein-coding mRNA after completion of pre-mRNA splicing

intron

non-protein-coding intervening sequences that are spliced from mRNA during processing

5' cap

modification added to the 5' end of pre-mRNAs to protect mRNA from degradation and assist translation

poly-A tail

modification added to the 3' end of pre-mRNAs to protect mRNA from degradation and assist mRNA export from the nucleus