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Section 7: Gene Expression
Chapter 10
61
Chemistry
Undergraduate 1
10/19/2012

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Term
One Gene-One Poypeptide
Definition
oversimplification;idea that each gene in the genome encodes only a single polypeptide--that there is a one-to-one correspondence between genes and polypeptides
Term
transcription
Definition
process of copying information in a DNA sequence (a gene) into a coimplementary RNA sequence
Term
translation
Definition
process of creating the amino sequence of a polypeptide from the RNA sequence of transcription
Term
messenger RNA
(mRNA)
Definition
travels from the nucleus to the cytoplasm, where it is translated into a polypeptide
Term
ribosomal RNA
(rRNA)
Definition
catalyzes peptide bond formation between amino acids to form a polypeptide
Term
transfer RNA
(tRNA)
Definition
can bind a specific amino acid and can recognize a specific sequence of nucleotides in mRNA through complementary base pairing
*recognizes which amino acid should be added to a growing polypeptide chain next
Term
transcription requires...
Definition
a) DNA template for complementary base pairing
b) appropriate nucleoside triphosphates (ATP GTP, CTP, UTP)to act as substrates
c) RNA polymerase enzyme
Term
RNA polymerase
Definition
catalyze the synthesis of RNA from DNA template
*only one kind in bacteria and archea
*several kinds in eukaryotes
Term
common structure of RNA polymerase
Definition
processive; single enzyme--template binding event results in the polymerization of hundreds of RNA nucleotides
*DO NOT REQUIRE A PRIMER
Term
promoter
Definition
special DNA sequence to which RNA polymerase binds very tightly
*"tell" RNA polyermase where to start transcription and which of the two DNA strands to transcribe
Term
transcription initiation site
(transcription start site-TSS)
Definition
where transcription begins
*located on the promoter
Term
elongation
Definition
process of RNA polymerase unwinding the DNA and reading the template strand in the 3'-to-5' direction
Term
termination
Definition
particular base sequences specify transcription termination
Term
coding regions
Definition
sequences within a DNA molecule that are expressed as proteins
Term
introns
Definition
noncoding sequences of a gene
*intervening regions;interrupt coding region
Term
exons
Definition
expressed regions interspersed with the introns
Term
pre-mRNA
Definition
primary mRNA transcript
*where introns and exons appear
*introns are removed by the time the mature mRNA leaves the nucleus
Term
pre-mRNA processing
Definition
involvies cutting introns out of the pre-mRNA transcript and splicing together the exon transcripts
Term
nucleic acid hybridization
Definition
methoed that originally revealed the existence of introns
involves 2 steps:
a) DNA to be analyzed is denatured by heat to break hudrogen bonds btwn base pairs and separate 2 strands
b) singled stranded nucleic acid from other source(probe) is incubated with denatured DNA; if probe has similar DNA sequence, it will form double helix by hydrogen bonding the bases
Term
RNA splicing
Definition
removes introns and splices exons together
Term
consensus sequences
Definition
short stretches of DNA that appear with little variation ("consensus") in many different genes
Term
small nuclear ribonucleoprotein particles
(snRNP)
Definition
complex of an enzyme and a small nuclear RNA molecule, functioning in RNA splicing
*bind consensus sequences in RNA splicing
Term
spliceosome
Definition
large RNA-protein complex; cuts pre-mRNA, releases introns, and joins exons together to produce mature mRNA
Term
ribonucleases
Definition
enzymes that break down RNAs in a 5'cap
Term
codon
Definition
each sequence of 3 nucleotide bases along the mRNA polynucleotide chain
*specifies a particular amino acid
*each in mRNA is complementary to corresponding triplet of bases in DNA from which it was transcribed
Term
start codon
Definition
initiation signal for translation
Term
stop codon
Definition
termination signals for translation; when translation machinery reaches one of these codons, translation stops and the polypeptide is released from translation complex
*UAA, UAG, UGA
Term
anticodon
Definition
3 nucleotides in tRNA that pair with a complementary triplet (a codon) in mRNA;
located about midpoint on tRNA polynucleotide chain; triplet of bases; complementary to mRNA codon for particular amino acid that tRNA carries
Term
A (amino acid) Site
Definition
where the charged tRNA anticodon binds to the mRNA codon, lining up the correct amino acid to be added to teh growing polypeptide chain
Term
P (polypeptide) Site
Definition
where the tRNA adds its amino acid to the polypeptide chain
Term
E (exit) Site
Definition
where the rRNA, having given uup its amino acid, resides before being release from the ribosome and going back to the cytosol to pick up another amino acid and begin the process again
Term
ribosome fidelity function
Definition
ensures that a charged tRNA with the correct anticodon binds to the appropriate codon in the mRNA
Term
polyribosome
(polysome)
Definition
assemblage consisting of a strand of mRNA with its beadlike ribosomes and their growing polypeptide chains
Term
protein synthesis always begins...
Definition
on free ribosomes floating in the cytoplasm
*"default" location for protein is cytosol
Term
signal sequence
(signal peptide)
Definition
short stretch of amino acids that indicates where in the cell the polypeptide belongs
*directs the protein to a particular organelle
*proteins destined for different locations have different signals
*binds to specific receptor protein at surface of organelle
Term
polyproteins
Definition
long polypeptides containing the primary sequences of multople distinct proteins
Term
gene
Definition
unit of hereditary;
used as the unit of genetic function which carries the info for a polypeptide or RNA
Term
gene expression
Definition
process by which information from a gene is used in the synthesis of a functional gene product
Term
central dogma of molecular biology
Definition
gene expression;
describes the way genetic information is expected to be transferred in a single direction through a biological system
Term
transcription
Definition
process of creating a complementary RNA copy of a sequence of DNA
Term
reading frame
Definition
3'-5'
*builds 5'-3'
Term
transcription factor
Definition
(sometimes called a sequence-specific DNA-binding factor)
*protein that binds to specific DNA sequences, thereby controlling the flow (or transcription) of genetic information from DNA to mRNA
Term
polyadenylation
Definition
addition of a poly(A) tail to an RNA molecule
Term
primary transcript
(pre-mRNA)
Definition
initial gene transcript before it is modified to produce functional mRNA
Term
mature mRNA
Definition
transcript of a region of one of the strands of DNA; carries info(as a sequence of codons) for the synthesis of one or more proteins
Term
mRNA splicing
Definition
primary transcript contains both introns and exons
splicing removes introns
the exons are then joined together in a continusous coding sequence of nucleotides
Term
alternative splicing
Definition
process of generating different mature mRNAs from a single gene by splicing together different sets of exons during RNA processing
Term
spliceosome
Definition
RNA-protein complex that splices out introns from eukaryotic pre-mRNAs
Term
charging reaction
Definition
process of loading tRNA with the amino acid
*aminoacyl-tRNA synthetase
Term
aminoacyl-tRNA synthetase
Definition
enzyme that catalyzes the esterification of a specific amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA
*simply attaches the accurate amino acid onto the corresponding tRNA
Term
ribosome
Definition
small particle in the cell that is the site of protein synthesis
Term
peptidyl transferase
Definition
catalytic function of large ribosomal subunit
consists of 2 rxns:
a)breaking bond btwn an AA and its rRNA in P site
b)forming peptide bond btwn that AA and AA attached to tRNA in A site
Term
release factor
Definition
protein that allows for the termination of translation by recognizing the termination codon or stop codon in a mRNA sequence
Term
wobble
(wobble pairing)
Definition
phenomenon that the cell gets by with about 2/3 of the total 61 different tRNA species becuase the specificity for the base at the 3' end of the codon (and the 5' end of the anticodon) is not always strictly observed
Term
silent mutation
Definition
change in a gene's sequence that has no effect on the amino acid sequence of of a protein becuase it occurs in noncoding DNA or because it does not change the amino acid specified by the corresponding codon
Term
mutation
Definition
change in the genetic material not caused by recombination
Term
missense mutation
Definition
change in a gene's sequence that changes the amino acid at that site in the encoded protein
Term
nonsense mutation
Definition
change in a gene's sequence that prematurely terminates translation by changing one of its codons to a stop codon
Term
frameshift mutation
Definition
addition or deletion of a single or two adjacent nucleotides in a gene's sequence
*results in the misreading of mRNA during translation and the production of a nonfunctional protein
Term
Insertion
Definition
addition of one or more nucleotide base pairs into a DNA sequence
Term
Deletion
Definition
part of a chromosome or a sequence of DNA is missing
*loss of genetic material
*any number of nucleotides can be deleted, from a single base to an entire piece of chromosome
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