Colloquia questions and answers April 8, 2005
1. In which molecular processes are the following proteins involved?
(answer as in the following example: DNA polymerase -- Replication, DNA repair)
a) DNA ligase -- Replication, DNA repair, recombination
b) Telomerase -- Replication
c) Aminoacyl tRNA synthetase -- Translation
d) RNA polymerase -- Transcription
e) Chaperones -- Polypeptide processing (folding)
f) PolyA polymerase -- Transcription/RNA processing
g) sigma70 -- Transcription
h) Elongation factor Tu (EF-Tu) -- Translation
2. Define briefly (1-5 sentences) the following terms:
a) Chromatin -- Complex of genomic DNA and chromosomal proteins
b) Nucleosome -- Unit in nucleus consisting of histones and DNA
c) Repetitive DNA -- repeated DNA sequences (tandem, interspersed)
d) Promoter -- site of RNA polymerase binding
e) Enhancer -- DNA sequence that enhances transcription
f) Organelles -- Plastids and mitochondria (contain DNA)
g) Nonsense mutation -- changes an aa codon into a stop codon
3.
a) Name at least 5 proteins that bind to DNA. (e.g. histones, RNA polymerase,
DNA polymerase, lac repressor, restriction endonucleases, sigma 70, etc)
b) Describe briefly (1-3 sentences) the function of the proteins you have chosen.
c) Explain how DNA-binding proteins find their specific binding sites and how
the proteins interact with the DNA double helix. (Contact with major or minor
groove, hydrogen bonding with bases, page 252)
4. a) List RNA processing events and mention which of the events are specific to
eukaryotes or prokaryotes.
(end modification -eukaryotes-archaebacteria, intron splicing-eukaryotesprokaryotes, chemical modification -eukaryotes-prokaryotes, editingeukaryotes-prokaryotes, cutting eukaryotes-prokaryotes)
b) Which processing events are specific for messenger RNA? (end modification,
editing)
c) Explain the role of snoRNA (small nucleolar RNA) in ribosomal RNA
processing.
(Methylation of rRNAs in the nucleolus, page 303)
5. a) Describe how transcription is terminated in bacteria. (rho-(in)dependent, page
275)
b) Give an example in which termination of transcription is regulated.
(Attenuation. Antitermination, page 280)
c) What kind of processing can prokaryotic RNAs undergo after transcription?
(cutting, chemical modification, degradation, splicing)
d) What is RNA editing? (Nucleotide change in mRNA, page 303)