AP Biology Chapter 17: From Gene to Protein Flashcards

DNA
Terms Definitions
gene expression
Process by which DNA directs protein synthesis
Includes two stages, transcription and translation
agar
Moist support medium for bacteria to grow on
one gene-one enzme hypothesis
The function of a gene is to dictate the production of a specific enzyme
one gene-one polypeptide hypothesis
Many proteins are constructed from two or more different polypeptide chains, and each polypeptied is specified by its own gene
*NOTE* not entirely accurate- some genes code for RNA molecules that are never translaated into protein
transcription
The synthesis of RNA under the direct of DNA, providing a template for assembling a sequence of RNA nucleotides
Occurs in the nucleus
messenger RNA
mRNA
A transcript of the gene's protein-building instructions
Carries a genetic message from the DNA to the protein-synthesizing machinery of the cell
translation
Actual synthesis of a polypeptide, which occurs under direction of mRNA
The cell must translate the base sequence of an mRNA molecule into the amino acid sequence of polypeptide
Occurs in the ribosome
ribosomes
Sites of translation
Complex particles that facilitate the orderly linking of amino acids into polypeptide chains
pre-mRNA
A strand transcripted from DNA before it has undergone RNA processing
RNA processing
Modification of RNA before it leaves the nucleus
Process unique to eukaryotes
primary transcript
An initial RNA transcript
Also called pre-mRNA when transcribed from a protein-coding gene
Occurs in the nucleus
triplet code
The genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, three-nucleotide words
EX. AGT on DNA results in placement of the amino acid serine on a polypeptide
template strand
One of the two DNA strands that provides the template for ordering the sequence of nucleotides in an RNA transcript
codons
mRNA base triplets
Written in the 5' → 3' direction
AUG
Start codon
UAA UAG UGA
Stop codons
reading frame
The way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons
RNA polymerase
Enzyme that pries the two strands of DNA apart and hooks together the RNA nucleotides as they base-pair along the DNA template
Can only assemble a polynucleotide in its 5' → 3' direction
Able to start a chain from scratch, without a primer
promoter
DNA sequence where RNA polymerase attaches and initiates transcription
terminator
In prokaryotes, the sequence that signals the end of transcription
transcription unit
The stretch of DNA that is transcribed into an RNA molecule
transcription factors
In eukaryotes, a collection of preteins that mediate the binding of RNA polymerase and the initation of transcription
Only after attached to the promoter does RNA polymerase II bind to it
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase II nound to the promoter
TATA box
A crucial DNA promoter containing the nucleotide sequence TATA, about 25 nucleotides upstream from the transcription start point
5' cap
The end first transcribed is capped off with a modified form of a guanine nucleotide after transcription of the first 20 to 40 nuvleotides
poly-A tail
At the 3' end, an enzyme adds 50 to 250 adenine nucleotides
RNA splicing
In the eukaryotic nucleus, the removal of a large part of the RNA molecule that is initally synthesized
Introns
Noncoding segments of the nucleic acid that lie between coding regions are called intervening sequences
Exons
A coding region of a eukaryotic gene
Exons, which are expressed, are seperated from each other by introns
Spliceosome
Several different snRNPs join with additional proteins to from an even larger assembly
Almost as big as a ribosome
Interacts with certain sites along an intron, releasing the intron and joining together the two exons that flanked the intron
Ribosyme
RNA molecules that function as enzymes
Alternative RNA splicing
A number of different genes are known to give rise to two or more different polypeptides, depending on which segements are treated as exons during RNA processing
Domains
Proteins often have a modelular architecture consisting of discrete structural and functional regions
One of, of an enzymatic protein, might include an active sight, while another might attach the protein to a cellular membrane
Transfer RNA
tRNA
The interpreter of the message in the codons along an mRNA
The function is to transfer amino acids to a ribosome
Anticodon
A nucleotide triplet at one end of a tRNA which base-pairs with a complimentary codon on mRNA
Aminoacyl-tRNA synthase
An enzyme that joins each amino acid to a specific tRNA (specific for each)
Wobble
A violation of the base-pairing rules in that the third nucleotide (5') of a tRNA anitcodon can form hydrogen bonds with more than one kind of base in the third position (3') of a codon
Ribosomal RNA
rRNA
The most abundant type of RNA, which together with proteins forms the structure of ribosomes
P site
Holds the tRNA carrying the growing polypeptide chain
A site
Holds the tRNA carrying the next amino acid to be added to the chain
E site
tRNA leaves the ribosome from
Polyribosomes
Strings of ribosomes along one mRNA strand
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