Molecular II Flashcards
nucleotide excision repair
endonuclease release damaged base
DNA polymerase and ligase fill and reseal
repair bulky lesions
occur in G1
defective nucleotide excision repair
xeroderma pigmentosa
prevent repair of pyrimidine dimers (UVB damage)
base excision repair
base specific glycosylase
-create site without pur or pyr
AP-endonuclease - remove one or more nucleotides - cleaves 5’ end
lyase cleaves 3’ end
DNA polymerase beta - fills gap and DIA ligase seals it
throughout cell cycle
mismatch repair
newly synthesized strand recognized
-mismatched nucleotides removed - gap filled and sealed
G2 phase of cell cycle
defective in hereditary nonpolyposis colorectal cancer
mismatch repair
nonhomologous end joining
bring together 2 ends of DNA fragments repair ds breaks
mRNA is read
5’ > 3’
direction DNA and RNA synthesis
DNA and RNA - both synthesized 5 > 3
5’ end - high energy bond - tri-P
protein synthesis direction
N-terminus to C-terminus
start codon
AUG
stop codon
UGA, UAA, UAG
fMet
prokaryote start codon
stimulate neutrophil chemotaxis
methionine
start codon - AUG - AA
promoter
site where RNA polymerase II and other transcription factors bind DNA upstream gene locus
AT rich - TATA box
enhancer
further upstream from promoter (TATA)
-alter gene expresion
silencer
site where gene repressor binds
RNA polymerse I
makes rRNA
RNA polymerase II
makes mRNA - largest RNA
RNA polymerase III
makes tRNA - smallest RNA
a-amanitin
in amanita phalloides - death cap mushroom
inhibit RNA polymerase II - mRNA synthesis
severe hepatotoxicty
rifampin MOA
inhibit RNA polymerase
actinomycin D
inhibit RNA polymerase
RNA processing - after transcription
occus in nucleus
1 - capping 5’ end - 7 methylguanosine cap
2 - polyadenylation 3’ end - 200 As
3 - splicing out introns
capped, tailed, spliced = mRNA
cytoplasmic P-bodies
mRNA quality control
exonucleases, decapping enzymes, microRNAs
snRNP
involved in splicing pre-mRNA
lariat shaped loop generated
-remove intron - join 2 exons
anti-smith antibodies
Abs to spliceosomal snRNP
specific for SLE
anti-U1 RNP Ab
associated with mixed CT disease
alternative splicing
different exon combination of single mRNA
beta-thalassemia
abnormal splicing variant
tRNA
CCA at 3’ end opposite anticodon - binds the amino acid
anticodon loop
T-arm - contains thymine, pseudouracil, cytosine - for tRNA ribosome binding
D-arm - dihydrouracil residues - for tRNA recognition by correct aminoacyl tRNA synthetase
charging of tRNA
aminoacyl tRNA synthetase uses ATP to bind amino acid to CCA 3’ end of tRNA
wobble
accurate base pairing only required first 2 nucleotide positions of mRNA codon
codon difference position 3 “wobble” may code for same AA - degeneracy of code
steps protein synthesis
initiation
elongation
termination
initiation
by GTP hydrolysis
initiation factors assemble 40S ribosome subunit with initiator tRNA
-released when mRNA and 60S subunit assemble with complex
eukaryote ribosomes
40S and 60S
prokaryote ribosomes
30S and 50S
elongation
aminoacyl tRNA binds to A site
rRNA catalyzes peptide bond formation - transfer growing polypeptide to AA in A site
ribosome advances 3 nucleotides toward 3’ end of mRNA - moving peptidyl tRNA to P site (translocation)
A site
incoming aminoacyl-tRNA
P site
accomodate growing peptide
E site
holds empty tRNA as it exits
termination
stop codon recognized by release factor
polypeptide released from ribosome
protein synthesis ATP and GTP
ATP - activation - charging
GTP - translocation
trimming
remove N or C terminal propeptide from zymogen
covalent alterations of peptide
phosphorylation glycosylation hydroxylation methylation acetylation ubiquitination
chaperone proteins
intracellular proteins involved in facilitating protein folding
yeast - Hsp60 - expressed at high temp - prevent protein denaturing/misfolding
