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BMSC 220 pt 2

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tasnimjaisee's version from 2017-10-26 05:22

Lecture 6 pt 2

Question Answer
When is 7-methylguanosine cap is first added?During the modification of the 5' end of a transcript
7-methylguanosine cap is composed of?GTP modified by methyl group
A poly-A tailTract of 200 adenine neucleotides added to 3' ends of mRNAs
PolyadenylationAdd poly-A tail to a pre-mRNA directed by mRNA 3’ end
What do Poly-A tails help regulateTranslation and mRNA stability
Changes in the length of the poly-A tail initiate?translation of the dormant maternal mRNA in embryos
snRNAsform the RNA component of the spliceosome
snRNAs assist in targetting snRNPS to?splice junctions through hybridization to RNA transcript
are snRNAs catalytic or anabolytic?Catalytic
some RNAs have been shown to be self-splicing, whereby.....an intron carries out the actual splicing reaction
In Drosophila what does alternative splicing determine?gender
Alternative splicingCreates multiple different, but related, proteins from the same gene
Each human gene yields an average of how many alternatively spliced mRNAs?6
SR splicing factors (SR proteins) bind to?exons to direct splicesomes
Which proteins assist in determining the final “choice” of exons?SR
splice factor that recognizes the branch pointU2AF
4 sets of alternative exons, with a single exon from each set being incorporated into the spliced mRNADscam
Dscamcell surface adhesion molecule important in allowing neurons to find their target cells
Which RNAs are cleaved post-transcription?tRNA and rRNA
Between 5’ and 3’ end of tRNA, which are cleaved as part of the processing?Both
What is 5’ end of eukarayotic tRNA is cleaved specifically byRNase P
What is 3’ end of eukarayotic tRNA is cleaved specifically byconventional RNase with CCA added to the end facilitating AAs
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Lecture 7 pt 1

Question Answer
nucleotide → nucleotideTranscription
nucleotide → amino acidsTranslation
Translation is carried out on ____, with ____ serving as adaptorsribosomes - tRNAs
genetic code is ___ codetriplet
mRNA read in which direction?5' ℗ group on the ribonucleotide sugar to 3' OH end of the mRNA
the first amino acid is?methionine
Codon on mRNA base pairs with ___ on tRNAanticodon
aminoacyl tRNAtRNA with a specific amino acid covalently bound at 3' end
Where is the anticodon locatedtRNA
Where is the codon locatedmRNA
rRNAs form complex 3-dimensional ____ structuressecondary
ribosomes =Protein + rRNA Both contribute to tertiary structure of ribosome
Ribosome assembly within the nucleolus of eukaryotic cells (3)imported to the nucleolus - attach to pre-rRNA - pre-rRNA splits in 2; 40S and 60S
tRNAs are synthesized by?RNA polymerase III
tRNAs, possess which unique 3 nucleotidesanticodons
tRNAs have which characteristic structurescloverleaf
Three steps of tRNA processingRNA cleavage - covalent addition of CCA - base modification
Three steps to “charge” a tRNAActivate AA - Add AA to tRNA - Proper folding brings AA to ribosome
Two points for specificity of amino acid incorporation into a protein during translation at the tRNA levelMatch AA to tRNA - Correct base-pairing of codon and anticodon
approx. ___ different tRNAs40
Monocistronic (2)One gene codes for one protein - Eukaryotic genome
Polycistronic (2)One gene codes for one protein - Prokaryotic genome
Translation occurs in three stagesInitiation - Elongation - Termination
In prokaryotes, an mRNA sequence called?Shine-Dalgarno sequence
What do Shine-Dalgarno sequence bind to?complementary base pairs in the 16S rRNA
In eukaryotes, the SMALL ribosomal subunit (40S) binds to?5' m7G cap of mRNA and 40s + initiation complex at START codon
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Lecture 7 pt 2

Question Answer
Initiation of translation in eukaryotic cells40S/eiFs/tRNAmet meet mRNA & binds 5’m7G cap - Finds AUG - 60S attaches and 40s and trna stays
The elongation stage of translationAPE
What do elongation factors complexed to GTPs, escort?aminoacyl tRNA to ribosomes
Translation- elongation stepsCharged tRNA comes to meet tRNAmet at AUG - Peptide bond - AtoP
Cystic fibrosis (FYI) occurs due to a mutation in the?CFTR protein
are PTMS reversible?Yes
are protein cleavages reversible?No
Why are carbohydrate additions important?protein folding and targetting
Two major pathways of protein degradation in eukaryotic cellsUbiquitin-proteasome pathway - Lysosomal proteolysis
UbiquitinPTM used in eukaryotic cells that targets cytosolic and nuclear proteins for rapid proteolysis
Proteasomesdegrade polyubiquinated proteins.
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Lecture 8

Question Answer
2 major pathways of protein sortingi) cytosolic pathway ii) secretory pathway
Ribosomes are located in the?cytosol
Targets of cytosolic pathway Nucleus - Mitochondia - Chloroplast - Peroxismes
cytosolic pathway: Starts in ___; Ends in ___Cytosol - cystosol
secretory pathway: Starts in ___; Ends in ___Cytosol - ER
Targets of secretory pathwayEndoplasmic reticulum, Golgi apparatus, lysosome
rough ER (RER)protein metabolism
smooth ER (SER)lipids
entry point for most proteins into the secretory pathwayRER
C terminus (carboxyl terminus)end of peptide
N terminus (amino terminus)start of peptide
Signal recognition particles, or SRPsbind to signals in the growing protein while the proteins is still being translated
SRP composed ofsmall cytoplasmic non-coding RNA and proteins
SRP receptors are proteins on the membrane of the?endoplasmic reticulum
Transloconmembrane channel [SEC] - signal sequence transported into ER
How does a signal sequence target a protein to the ER?signal sequence->SRP->SRPR->translocon->peptidase
BiPmolecular chaperone in the ER
both passage into the ER lumen, and ER membranes, involves the action of?molecular chaperones
What does transmembrane sequence in the polypeptide being synthesized do?Stops polypeptide from entering - changes translocon conformation
ER is ____ equivalent to the exterior of the celltopologically
What face of Golgi = closest to ER?Cis
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