Lesson 5: Transcription Key Terms

DNA transcription

the process a cell undergoes when it needs a particular protein, nucleotide sequence of the DNA is copied into RNA

RNA polymerase

enzyme that catalyzes the synthesis of an RNA molecule on a DNA template from ribonucleoside triphosphate precursors

mRNA (messenger RNA)

RNA molecule that specifies the amino acid sequence of a protein

noncoding RNAs

RNA molecule that is the final product of a gene and doesn’t code for protein; serve as enzymatic, structural, and regulatory components for the cell

promoter

nucleotide sequence in DNA to which RNA polymerase binds to begin transcriptiontr

transcription bubble

a temporary, unwound region of DNA where the double helix opens up so RNA polymerase can read the genetic code and build the RNA

elongation

the stage where RNA polymerase moves along the DNA template strand and builds a growing complementary RNA chain

transcription factor

any of the proteins whose assembly at all promoters of a given type is required for the binding and activation of RNA polymerase and the initiation of transcription

initiation

the stage where RNA polymerase binds to the promoter on DNA to begin copying a gene into RNA

TATA box

sequence in the promoter region of many eukaryotic genes that binds a general transcription factor (TFIID) and hence specifies the position at which transcription is initiated

terminator

signal in bacterial DNA that halts transcription; in eukaryotes, transcription terminates after cleavage and polyadenylation of the newly synthesized RNA

termination

the stage where the RNA polymerase stops copying the gene, releases the newly made RNA strand, and detaches from the DNA template

elongation factors

specializes proteins that bind to RNA polymerase during elongation to regulate, assist, and speed up the synthesis of the RNA strand

transcriptional activator

specialized protein that binds to specific DNA sequences to increase the rate of gene transcription

enhancer

a short specific region of DNA that binds transcription factors to increase the rate of transcription for a target gene

topoisomerase

enzyme that binds to DNA and reversibly breaks a phosphodiester bond in one or both strands; I creates single-strand breaks, II makes a double-strand break

DNA supercoiling

a conformation with loops or coils that DNA adopts in response to superhelical tension; conversely, creating various loops or coils in the helix can create such tension

DNA gyrase

an enzyme that introduces negative supercoils into DNA to relieve winding strain (specialized topoisomerase II)

RNA splicing

process in which intron sequences are excised from RNA transcripts

intron

noncoding region of a eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing

exon

segment of a eukaryotic gene that consists of a sequence of nucleotides that will be represented in mRNA or in a final transfer, ribosomal, or other mature RNA molecule. In protein-coding genes, exons encode the amino acids in the protein

polyadenylation signal

specific sequence of nucleotides in a pre-mRNA transcript (most commonly AAUAAA in eukaryotes) that tells cellular machinery where to cleave the RNA and add a protective chain of adenine nucleotides, known as the poly(A) tail

capping

the addition of a special chemical tag to the front end of a new RNA molecule while it is being made during transcription (5’ cap)

polyadenylation

the addition of a long chain of adenine nucleotides—called a poly(A) tail—to the 3' end of an RNA transcript during gene expression

small nuclear RNAs (snRNAs)

small RNA molecules that are complexed with proteins to form the ribonucleoprotein particles (snRNPs) involved in RNA splicing

spliceosome

large assembly of RNA and protein molecules that performs pre-mRNA splicing in eukaryotic cells