EXAM 2 Flashcards
Describe or draw a schematic explaining the rho-independent termination of transcription mechanism.
Formation of stem-loop, release of RNA polymerase and RNA from DNA template.
How does a Eukaryotic cell compensate for its relatively slow replication process (incorporation of 50 nucleotides per second)?
Multiple origins of replication.
Explain how microRNA can contribute to regulating protein expression. Explainyour answer (schematic showing the different steps and components)
Goes from pri-miRNA to processing by Drosha (splicing) to pre-miRNA, then maturation by Dicer (splicing) and Ago proteins (AGO 1-4) and un-winding to make single-strand RNA (RNA helicase activity) that will bind to target sequences and promote mRNA degradation and/or prevent translation by hindering ribosome progression
How are eukaryotic mRNAs 5’end protected from degradation? Describe the molecular components involved.
Cap 7methyl guanosine at 5’end with 5’ to 5’ phosphodiester bond. RNAse does not recognize this set of features.
How does Nucleotide-Excision Repair (NER) remove Thymine Dimers. Describe the main steps necessary for this repair to take place.
Cleavage 5’ and 3’
Unwinding by helicase
Filling by DNA pol and sealing by ligase.
A strain of Bacteria with a conditional mutation of Single-Strand Binding Proteins, which can be activated by a specific trigger, has been generated.
What cellular functions will be affected when this set of mutations is triggered?
Which proteins are SSBP?
Replication: Maintenance of SS structure,
Recombination and repair: RecA, RuvA
Aminoacyl tRNA synthetases are enzymes that
attach amino acids to specific transfer RNAs.
What are the composition, and function of the Signal Recognition Particle?
SRP is a ribonucleoprotein containing a 300 nt srpRNA or 7S RNA (acting as a necessary scaffold) plus 6 proteins.
Role binding to signal sequence of peptide or protein, arrest translation and bind to receptor protein on the ER. Srp RNA interacts with ribosome.
What are the differences between a ”cis” and a “trans” element?
Give me an example for each type of element
“Cis” elements are DNA sequences. Trans elements are proteins binding to “cis’ elements.
Cis element: Promoter region
Trans element: TATA-binding protein.
What is the composition of a Prokaryotic ribosome?
2 sub-units a 30S and a 50S
30S sub-unit made of 16S rRNA plus 2—21 proteins
50S sub-unit made of 23S and 5S rRNA plus 34 proteins
What is the role of snoRNP (small nucleolar Ribo Nucleic Particle)?
snoRNP are composed of sno RNA plus 8-10 proteins.
They are involved in rRNA processing and modifications (addition of CH3 groups, ribosylation, modification of uridine to pseudo-uridine) and cleavage of pre rRNA to mature rRNA.
What is the role of the protein Hsp70?
Hsp70 is a chaperone which primary function is to coat newly synthesized protein and to promote proper folding.
Describe the different steps required for DNA mismatch Repair in bacteria?
- MutS, MutL, MutH bind to the old strand of mismatch.
- MutH cleaves the unmodified strand opposite a site of methylation.
- MutS, MutL, helicase, and exonuclease then excise the portion containing the mismatch.
- DNA polymerase then fills in the gap and then DNA ligase seals the backbone.
How does chromatin affect DNA Repair? How do Eukaryotic cells manage the chromatin effect to allow DNA repair?
Chromatin, through steric interactions, will impede DNA repair.
Nucleosomes prevent access to the DNA region which needs to be repaired. To open access to chromatin, the cells will make use of chromatin remodeling complexes, which are recruited through interactions with DNA-binding proteins and/or specific modifications of histones (g-H2A-X for example is used to tag double-strand breaks)
