1 Exam 3 Biol 213 Molecular Cell Biology Fall 2012 Neatly printed name_______________________________________Signature__________________________________ Please note that there are 105 points on this exam but the maximum score you can receive is 100. The space provided for each question should be sufficient for your answers. Questions 1-15 are worth 3 points each. Circle your answer. 1. In human nuclear DNA (a) there are linear chains of nucleotide triphosphates (b) the number of A/T base pairs equals the number of G/C base pairs (c) there are no 3’ ends (d) there are no 5’ ends (e) none of the above answers are correct 2. In general, histone phosphorylation (a) increases the replication rate (b) decreases the replication rate (c) increases the transcription rate (d) decreases the transcription rate (e) none of the above answers are correct 3. The Meselson-Stahl experiment showed that (a) DNA replication starts at an origin of replication (b) protein synthesis starts with an amino acid forming a hydrogen bond to a tRNA (c) DNA is the carrier of genetic information (d) DNA replication is semiconservative (e) protein synthesis starts with an amino acid being covalently linked to a tRNA2 4. Okazaki fragments (a) are found only in bacterial cells (b) are found only in eukaryotic cells (c) involve a RNA primer and a DNA template (d) involve a DNA primer and a RNA template (e) are used to correct errors after transcription has occurred 5. To begin making RNA, bacteria use (a) sigma factors (b) an origin of replication (c) psychic friends (d) either a or b (e) a DNA primer 6. Transcription terminators (a) form a stem-loop structure in the RNA (b) form a stem-loop structure in the DNA (c) terminate transcription in bacteria but not eukaryotes (d) involve a UAA, UGA, or UAG codon (e) are only found at the ends of chromosomes 7. Shine-Dalgarno sequences (a) can cleave themselves but not ligate themselves (b) can ligate themselves but not cleave themselves (c) can cleave themselves and ligate themselves (d) function as pseudogenes (e) are not found in eukaryotic nuclear RNA 8. Which of the following does not occur before a eucaryotic mRNA is exported from the nucleus? (a) The ribosome binds to the 5’ cap. (b) The mRNA is polyadenylated at its 3’ end. (c) 7-methyl-G is added in a 5’ to 5’ linkage to the mRNA. (d) RNA polymerase dissociates. (e) Splicing out of introns in mRNA. 9. miRNA’s and siRNA’s (a) inhibit DNA polymerase (b) inhibit RNA polymerase (c) increase expression of the corresponding mRNA (d) regulate the final step in RNA splicing (e) decrease expression of the corresponding mRNA 10. Eukaryotic genes can have (a) multiple transcription factors bound to the promoter at any given time (b) only one transcription factor bound to the promoter at any given time (c) transcription factors on the 3’ end of the gene at any given time (d) multiple RNA polymerases bound to the promoter at any given time (e) multiple DNA polymerases bound to the promoter at any given time3 11. Antibiotics such as erythromycin block (a) DNA polymerases (b) RNA polymerases (c) transcription factors (d) tRNA synthases (e) ribosomes 12. Enhancers (a) are only found upstream of genes. (b) can be found upstream or downstream of genes. (c) need to be immediately adjacent to the AUG. (d) need to be immediately adjacent to the transcription start site. (e) need to be immediately adjacent to the kinetochore. 13. Which amino acid would you expect a tRNA with the anticodon 5’-CCA-3’ to carry? (a) proline (b) glycine (d) tyrosine (d) methionine (e) tryptophan 14. Gene transfer by plasmids (a) almost always cause cancer (b) are often passed to the offspring (c) are often found in bacteria (d) are not passed to the offspring (e) are often passed to the zygote cells 15. Single nucleotide polymorphisms (a) are often found in humans. (b) are rarely found in humans (c) are generally found in open reading frames (d) arise from gene duplications (e) arise from transposons 3 points 16. In the Hershey-Chase experiment, what was used to label protein, and what was used to label DNA? 3 points 17. Starting with a piece of doublestranded DNA, what other enzymes are needed before DNA polymerase can begin replication making a complementary strand? Hexilase, DNA primase for lagging strandDNA P32, protein S35for both lagging& leading strand, single stranded DNA-binding protein4 18. You are studying the yeast ADE3 gene. You have a small fragment of the middle of the coding region of the mRNA. The sequence of the fragment is CCGUAAGUGACGA 4 points a) What is the amino acid sequence of this part of the ADE3 protein? (remember that there is a codon table on page 1). Explain your answer. 4 points b) A mutant yeast expresses abnormally high level of the ADE3 protein. The mutation is due to changing a G to a C at one base pair in the ADE3 gene. What part of the ADE3 gene has probably been mutated? 7 points 19. Draw a line diagram of a typical bacterial mRNA. -name the key features at the 5’ and 3’ ends that distinguish this from a eukaryotic mRNA -indicate the two key codons -name the three regions of the mRNA 6 points 20. The ribosome is roughly half RNA and half protein. What are two other key enzymes in eukaryotic molecular biology that are part RNA, part protein? CCG? because in coding region. RNA polymerase 1 & 3Eukaryotic has 5' cap of 7-methylG, 3' of polyA tailKey is the start of Shine-Dalgarno Sequence & AUG5' untranslate, 3' untranslate, open reading fragmentPro, UAA is stop signno stop codon should be in the middle, CCG-UAA- is wrong, CGU-AAG-UGA also stop. only GUA-AGU-GAC can be rightmutation on promotersplisome, telomerasekey codon: start & stop5 6 points 21. Aciyclovir (Zovirax) is a frontline therapeutic for herpes, chickenpox, and shingles (caused by herpes virus). You are a pharmacist, and a patient has asked you what acyclovir does, and the mechanism of action. The patient knows some molecular biology. Please explain (draw diagrams if you want) -what acyclovir basically resembles -what happens to acyclovir in a cell infected with herpesvirus -what acyclovir does 9 points 22. Please draw the ‘central dogma’ of molecular biology. - name the