Nucleotides Exam 2-Leush

Name 2 protein-RNA complexes involved in transcription or translation
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Name 2 protein-RNA complexes involved in transcription or translation
1. Signal recognition particle (SRP)
2. Spliceosome (or snRNPs)
3. Ribosome
Which two statements about release factors are true?
1. They recognize stop codons
2. They are proteins
Which post translational modifications of lysine residues of histones discussed in class will affect gene expression and why?
1. Acetylation
2. Reduces electrostatic interactions between histones and DNA, thereby increasing the accessibility of DNA to transcription factors/RNA polymerase and consequently gene expression
Give two explanations why proinsulin is being made first and subsequently processed to insulin?
1. Guarantees that A and B chains are synthesized in a 1:1 ratio

2. Allows correct folding of the chains for correct disulfide bond formation
Give four examples of post translation modifications of protein.
1. Acetylation
2. Phosphorylation
3. Proteolytic Processing
4. Glycosylation
5. Protein Folding
In which type of RNA molecule would you expect to encounter dihydrouridin and pseudouridin?
tRNA
Describe how the translation start site is selected prokaryotes vs. eukaryotes.
1. Prokaryotes: Shine-Delgarno sequence upstream of AUG Start codon is recognized by the 3' end of 16S rRNA of the ribosome
2. Eukaryotes: eIF4 binds to 5' cap of mRNA and walks downstream. The first AUG encountered will be the Start codon
Define the terms repressor, operator, and promoter
Repressor: protein that binds to the operator sequence to inhibit gene transcription
Operator: DNA sequence to which the repressor binds
Promoter: DNA sequence to with RNA polymerase binds
What is the structural basis for the mode of action of the antibiotic puromycin?
1. Puromycin structurally resembles the 3' end of tyrosyl-tRNA and thus competes with aminoacyl-tRNAs
2. Amino group of puromycin can accept peptide to form peptide-puromycin, but transpeptidation cannot occur because of an amide bond between sugar and Tyr, leading to early termination
Define the terms transition, transversion, missense mutation, nonsense mutation, and silent mutation
Transition: purine-to-purine or prymidine-to prymidine mutation
Transversion: purine-to-prymidine mutation
Missense mutation: changes amino acid code
Nonsense mutation: introduces stop codon
Silent mutation: amino acid code remains unchanged
Name two characteristics of a peptide that would suggest that it is made nonribosomally.1. Presence of D-amino acids 2. Unusual amino acids 3. Modified amino acidsName two protein factors involved in the elongation cycle in prokaryotes.1. EF-Tu 2. EF-Ts 3. EF-GName three structural features unique to tRNA1. Anticodon 2. 3'-CCA acceptor arm of aminoacylation 3. Nucleosides are highly modified 4. Many non-Watson-Crick base pairs 5. 5' phosphateWhy can one tRNA recognize several degenerate codons?Wobble base pairs possible between mRNA codon and tRNA anticodonCorrelate the following protein factors with one of the 3 steps in ribosomal protein synthesis they are involved in.Factor Process Organism EF-Tu elongation/binding prokaryotes eIF-3 initiation eukaryotes EF-G elongation/translocation prokaryotes IF-1 initiation prokaryotes RF-1 termination/release prokaryotesWhich one of the following factors is required for binding of aminoacyl-tRNA during elongation in eukaryotes?EF-1αWhy is "Attentuation" as discussed in class a regulator mechanism that only exists in prokaryotes?This is a cooperative interaction between transcription and translation. Coupled transcription-translation only exists in prokaryotes where transcription and translation are not compartmentalized.As discussed in class. which covalent modification on the following biomolecules commonly affects gene expression in eukaryotes?Histone: acetlyation DNA: methylationGCU and GCC codons (5' -> 3') can be recognized by the same tRNA. Give one possible anticodon sequence of the tRNA indicate (3' -> 5' end).CGI (3' -> 5') = IGC (5' -> 3')