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January 23, 2009 Multiple choice questions (numbers in brackets indicate the number of correct answers) Nucleic acids were first isolated in the 17th century 18th century 19th century 20th century (1) The following are not components of DNA Pyridines Purines Sulfates Phosphate Deoxyribose (2) The DNA double helix is stabilized by Ionic bonds Covalent bonds Hydrogen bonds Hydrophobic interactions (2) The secondary structure of proteins is stabilized by Hydrophobic interactions Ionic bonds Hydrogen bonds Disulfide bonds (1) DNA is synthesized in 5’->3’ direction 3’->5’ direction in both directions (1) The major form of DNA in cells is A-DNA B-DNA C-DNA Z-DNA (1) Z-DNA Winds to the left Has a wider diameter than A and B-DNA Does not naturally occur in cells Has been studied extensively by Watson and Crick (1) The genetic code Is a “degenerate” code Consists of 60 codons Has three initiation codons Specifies the 20 standard amino acids Has four termination codons (2) The human nuclear genome Is about 2 billion bp in size Is split into 24 chromosomes Contains about 50,000 genes Is the largest genome known to date (1) RNA molecules Contain ribose instead of deoxyribose Are less abundant than DNA in cells Can be processed in different ways Are usually more than 3000 nucleotides long Are more stable than DNA molecules Transcriptomes Consist of RNA Consist of proteins Are translated into proteins Do not change in their composition Differ in different cell types Restriction endonucleases Are located in the nucleus Degrade DNA completely into nucleotides Bind to DNA Occur only in bacteria Are proteins Were discovered in the 1980s DNA ligases (2) (3) (3) Catalyze the formation of ß-glycosidic bonds Catalyze the formation of phosphodiester bonds Play a role in the process of transcription in cells Play a role in the process of translation in cells Require energy to function Are found in all living cells Reverse transcriptases Are DNA polymerases Are RNA polymerases Use DNA as template Use RNA as template Are viral enzymes Are essential enzymes in all eukaryotic cells (3) Ribosomal RNAs Make up ≈ 20% of all RNA in a cell Are involved in synthesis of proteins Are molecules that normally are not processed Bind ribosomal proteins (3) Mitochondrial genomes Are much smaller than nuclear genomes Are not found in all cells of a multicellular organism Are always circular Have a very high copy number compared to nuclear genomes (2) (2) Bacteriophages Are viruses Can infect bacteria and eukaryotic cells Have been used by Oswald Avery to show that DNA contains genes Have an average size of around 1 µm Consist of proteins and nucleic acid Agarose Is isolated from algae Is primarily used to separate proteins Is normally used at concentrations around 1% Forms pores of 10 - 30 nm in diameter in gels (2) (2) Total number of correct answers: 34 If time allows, please try also to answer the “Multiple choice” and “Short answer questions” at the end of chapters 1 and 2 of the GENOMES textbook.
