Chapter 17 Flashcards
transcription
is the synthesis of RNA under the direction of DNA, produces mRNA
Translation
is the synthesis of a polypeptide, which occurs under the direction of mRNA
ribosomes
site of translation
nuclear envelope
separates transcription from translation
template strand
3’ to 5’ DNA strand that provides a template for RNA transcripts made 5’ to 3’
mRNA base triplets
read 5’ to 3’, each codon specifies the amino acid in a growing polypeptide
3 stages of transcription
initiation, elongation, termination
initiation
signaled by promoters for the initiation of RNA synthesis, transcription factors and RNA polymerase II bound to a promoter; brings together mRNA, tRNA with the first amino acid, and the two ribosomal subunits
elongation
RNA polymerase moves along the DNA and untwists the double helix, 10 to 20 bases at a time; amino acids added one by one to preceding amino acid, each addition has proteins called elongation factors and occurs in 3 steps, codon recognition, peptide bond formation, and translocation
two ribosomal subunits
large and small; made of proteins and ribosomal RNA
p site
holds tRNA that carries the growing polypeptide chain
A site
holds tRNA that carries the next amino acid to be added to the chain
E site
exit site, where discharged tRNs leave the ribosome
chromatin modifying enzymes
provide initial control of gene expression by making a region of
DNA either more or less able to bind the transcription machinery
control elements
associated wit most eukaryotic genes, segments of noncoding DNA that help regulate transcription by binding certain proteins; the proteins they bind to are critical to the precise regulation of gene expression in different cell types
transcription factors
proteins required by eukaryotic RNA polymerase to initiate transcription
introns
long noncoding stretches of nucleotides that lie between coding regions
exons
eventually expressed after being translated into amino acid sequences
RNA splicing
removes introns and joins eons, creating an mRNA molecule with a continuous coding sequence
RNA processing
both ends of the primary transcript are usually altered; some interior parts of the molecules are cut out, and other parts spliced together
nucleotide cap
received by the 5’ end
poly A tail
received by the 3’ end
