Exam 3 Flashcards
Initiator proteins
breaks H bonds to initiate replication
Primer
short nucleotide sequence that initiates DNA polymerase binding
Primase
RNA polymerase that creates primers
For proofreading to take place…
DNA must be copied in 5 - 3’ direction
why is it 5’ to 3’
energy from triphosphate on oncoming 5’ end gives energy for reaction
Telomerase
Adds bases 5’ to 3’ to the lagging template strand
*Extends the template strand so DNA replication proteins can replicate
lagging strand and it does not shrink with each cell division.
Depurination
G lost
Deamination
C turns to U
Mismatch repair system
Excision - damage is
recognized and cut out by one of a
series of nucleases
resynthesis - original
DNA sequence is restored by a
repair DNA polymerase
Ligation - DNA ligase seals
the break left in the sugar–
phosphate backbone of the
repaired strand
Exonuclease
– remove bases from the end of a strand
Endonuclease
– remove bases from the middle/cut DNA or RNA
5’-3’ exonuclease activity
- Removing RNA primers made by primase
3’-5’ exonuclease activity
- Proofreading
Nucleases
– enzymes that remove nucleotides from DNA
Promoter v Terminator
Terminator transcribed, Promoted not
Promoter sequences at
-10, and -35 nucleotides down from start
Eukaryotic vs Prokaryotic regulatory proteins
Eukaryotic - multiple accessory proteins
- 3 RNA poly
Prokaryotic - one sigma factor
- 1 RNA poly
RNA poly 2
transcribes all proton coding genes
TFIID, TFIIH, and RNA poly II
TFIID - distorts DNA
TFIIH - opens up double helix
RNA Poly II - disassociates from other factors and starts transcription
Elongation Factors
Form a wedge on nucleosomes that allow RNA poly II to transcribe through proteins
cap and poly A tail
5’ cap Phosphate w/ modified guanine
Poly A tail
Effects from capping and polyadenylation
1) increase the stability of eukaryotic mRNA.
2) facilitate export to the cytosol
3) mark the molecule as an mRNA molecule
snRNP
recognizes splice sequences
U1, U2, U6
U1 recognizes the 5′ splice site
U2 recognizes the lariat branch-point site through
complementary base-pairing.
U6 then “double-checks” the 5′ splice site by displacing
U1 and base-pairing with the same intron sequence itself.
RNA synthesis location
membrane-less components in nucleus
snRNA and snRNP
small nuclear ribonucleoprotein used as functional unit of spliceosome
small nuclear RNA recognizes splice site
UUU codes for
phenylalanine
tRNAS match ____ to codons
amino acids
Aminoacyl-tRNA synthetase charges a tRNA with the correct ______ ____, requires ATP
Amino Acid
The genetic code is translated by…
aminoacyl-tRNA synthetases and tRNAs.
charging
Each synthetase couples a particular amino
acid to the proper tRNA
Translation step 1
charged tRNA carrying the next amino acid
to be added to the polypeptide chain binds to
the vacant A site
Translation step 2
polypeptide chain on site P attaches to A site to add to chain
Translation step 3
large subunit moves over the chain to open up the A site
Translation step 4
tRNA ejection from E site to allow process to repeat
Initiation of protein synthesis in eukaryotes requires…
translation initiation factors and a special initiator tRNA
Translation halts at a
Stop codon
*the binding of release factor to an A site bearing a stop codon terminates translation of an mRNA molecule.
A single prokaryotic mRNA molecule can encode
several different proteins.
Bacterial translation
can start at a variety of different locations allowing multiple different proteins from one RNA
small and large ribosomal RNA only form together after
small ribosomal subunit has bound to mRNA
tRNA have ________that is antiparallel to the codon
anticodons
Translation is initiated by a complex of:
- translation initiation factors
- initiator tRNA
- small subunit of the ribosome
Proteasome…
degrades proteins marked by ubiquitin
many proteins require _____ after translation
modifications to become functional
Protein modification
non covalent folding
Covalent
- phosphorylation
- glycosylation
The final concentration of each
protein depends on…
the rate of each step
depicted.
Regulation of gene expression allows for the
differences between cells with the same genome.
Many transcription regulators bind to DNA as _______, rather than monomers
dimers
Activator protein
binds to enhancer and attracts poly II
Repressor
decrease
transcription by blocking assembly or
preventing RNA pol moving forward.
Combinatorial Control
Combinations of a few transcription regulators can generate
many cell types during development.
