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BHCM 307 Exam II
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Explain why the genetic code is degenerate
because it is redundant
most aa have more than one codon
first 2 nucelotides are most important
Start and Stop codons
Start is AUG (Met)
3 stop codons no aa listed
Wobble
because third base pair isn't as important
There for several tRNAs for each aa
Inosine can bond with A, U, or C = wild card
Check pH question
:-)
aminoacyl- t RNA sythetases
at least one sythetase for each aa
catalyze reaction
aa + ATP -> aminoacyl-AMP +PP
i
aminoacyl-AMP + tRNA -> AMP + aminoacyl-tRNA
they are specific to the aa and tRNA
aa linked to 3' hydroxyl
Open Reading Frame
ORF
sequence starting with AT(U)G and ending with a stop codon
Translation In Eukaryotes
ATG is usually the initiator codon
1 mRNA = 1 protein
Shine-Dalgarno Sequence
sequence that binds to ribosomal RNA and initates translation by makin an initiation complex
In prokaryotes
can be anywhere in mRNA = can code for more than one protien
Chain initiation in Prokaryote
formation of initiation complex (mRNA, ribosomes subunits, initiation factors, fMet-tRNA)
Chain Elongation in Prokaryote
Ribosome attaches to P site and A site
Step 1
: aminoacyl-tRNA binds to A site and anticodon loop binds to next codon
Step 2
: peptide chain moves from P to A site
-catalyzed by peptidyltransferase
-forms new peptide bond
-proteins synthesized N to C
Step 3
: release tRNA at P site and translocation of peptidyl-tRNA from A to P
Chain termination in Prokaryotes
Release factors bind to A site with a stop codon
peptide is released from final tRNA hydrolysis
mRNA is relased
ribosomal subunits dissociate
cloning
isolating the gene in a form that can be replicated in abundance in another host
nucleases
enzymes that degrade nucleic acids
exonucleases
: degrade from 5' to 3' end
endonucleases
: degrade nucleic acids by cleaving at specific internal sequences
Developed by bacteria to kill virus DNA
Restriction endonucleases
cut DNA at specific sequences
usally palindromes
hydrolyze the phosphodiester backbone
recognition sequence
place were enzymes cleave
usually even numbered
size determines frequency
longer more rare 6 bp = relatively rare
Sticky ends
can rebind with H-base pairing
weak and easily comes apart
DNA ligase can can reform the phosiester covalent bond and make it strong
It is like molecular glue
Vectors
what DNA can be cloned into
Used to use
bacteriophages
to make single strand DNA
Now use
plasmids
circular DNA
Plasmids
Circular DNA
In bacteria
Carry their own origin of replication
carry antibiotic resistance genes
many convenient restriction enzyme sites for cloning
Engineered more sites
DNA RNA both neither
adenosine
both
DNA RNA both neither
ribose
RNA
Purines
hexose and pentose
pyrididines
hextose
DNA replication begins at the
origin
peptidyltransferase
enzyme encoded by ribosomes
makes new peptide bond
fMet transfers
formation of intitation complex
RNA
small ribosomal sub units
Initiation factor
fMet-tRNA
large ribosomal sub unit
cDNA
copy DNA
complementary DNA
synthesized in vitro by reverse transcriptase using mRNA as a template
represents genes expressed in a cell or tissue
There are cDNA libraries
cloning DNA in Plasmid vectors
digest wanted DNA and plasmid with same restriction enzyme
mix DNA and allow sticky ends to anneal
add DNA ligase and ATP
add mixture to antibiotic sensitive bacteria that can take up the DNA
grow in antibiotic
DNA electrophorese
DNA is negatively charged
smaller moves faster
ethidum bromide- makes it floress
dideoxy nucleotides
don't have the 3' or 2' OH
therefore end the sequence
if you know where it ends you can figure out the sequence
microray v. northern blot
microray
: does thousands at once
attaches them to a chip
tags and floresses them
northern blot:puts it on a nylon sheet
hybridizes it with DNA probe
PCR
uses taq polymerase
heat to 94 for 30 seconds
cool to ~55 for 30 seconds
heat to 74 for how ever long you want the bp
Author
MRK
ID
241358
Card Set
BHCM 307 Exam II
Description
Translation
Updated
2013-10-26T20:14:51Z
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