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39 Cards in this Set

  • Front
  • Back
Central Dogma-gene to protein
core belief of protein synthesis
gene=
protein=
mRNA=
cookbook
food
recipe
Central dogma states:
information flows in one direction: DNA-RNA-protein
Transcription:
production of mRNA f rom a DNA template
Translation
production of a proetin from an mRNA template by a ribosome
Prokaryotes:
mRNA from transcription is immediately translated without more processing or transport
RNA polymerase
enzyme that builds polymers of RNA in transcription
Eukaryotes
mRNA is created and processed (modified), mRNA travels to cytosol, ribosome binds to mRNA to translate into a protein
Crick and Brenner
determined that DNA is read in sets of 3 nucleotides for each amino acid
deciphering the genetic code
required determing how 4 nucleotides could encode more than 20 amino acids
codon
specific set of 3 nucleotides that translates for a specific amino acid
A-U
DNA-RNA
A-T
DNA-DNA
Transcription (3)
Initiation: RNA polymerase bonds to promoter
Elongation
Termination: RNA polymerase reaches terminator, mRNA transcript is released
A
T
C
G
U (replaces T in RNA)
A
G
C
DNA (3)
double stranded
deoxyribose sugar
uses T-A
RNA (3)
single stranded
ribose as sugar
uses U-A
Coding strand
DNA that matches mRNA
template strand
DNA being used to create mRNA
transcipt strand
mRNA strand being created
RNA polymerase (2)
uses info within the gene
-promoter:on/off switch
-terminator:end of gene
RNA processing (3)
1)enzymes in eukaryotic nucleus modify mRNA
2)both ends are usually altered
3)some interior parts are cut out and remaining parts are spliced together
Modification of mRNA (2)
-5' end recieves a modified nucleotide 5' cap
-3' end gets a poly-A tail
duty of modifications (3)
-facilitate the export of mRNA
-protect mRNA
-help ribosomes attach to the 5' end
Introns
noncoding DNA that have to be removed
Exons
DNA that is left that will actually be translated to make the protein
RNA splicing
removes introns and joins exons, creating the final mRNA molceule which travels to the cytosol
Translation (4)
-mRNA is translated into protein with tRNA
-Initiation
-Elongation
-Termination
tRNA (2)
-carries a specific amino acid on one end
-has an anticodon on the other end
anticodon
has complementary base pairs with the codon (3 nucleotides) on mRNA
structure of tRNA
tRNA molecules are lined up with codons on the mRNA by a ribosome
structure of Ribosome (3)
-A (amino site) binds the tRNA carrying the next amino acid
-P (peptide site) binds the tRNA attached to the growing peptide chain
--E (exit site) binds the tRNA that released the last amino acid
Step I: Initiation (4)
-small ribosome subunit binds to mRNA
-Initiator tRNA binds to mRNA
-Large ribosome subunit binds to tRNA
-requires GTP
Step II: Elongation: (2)
-Amino acids are added one by one to the preceding amino acid, which forms the protein chain
-each addition involves external proteins called elongation factors
-codon recognition
-peptide bond formation
-translocation
synthesis cycle
ejects the empty 1 to make way for a new one.
Step III: Termination
-occurs when a stop codon in the mRNA reaches the A site of the ribosome (cycle continues until this)
-Release factor causes the addition of water molecule instead of an amino acid which:
releases the polypeptide
causes the translation assembly to come apart
During and after synthesis:
a protein chain spontaneously coils and folds into its three-dimensional shape because proteins are made of amino acids which make them differ in shape
Additional modifications (2)
-activation by an enzyme that cleaves the protein
-several peptides may come together to form the subunits of a protein (hemoglobin)
point mutations
chemical changes in just one base pair of a gene
-base pair substitutions
-base pair insertions or deletions