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Exam 2 Genetics, Fall 2016 1. You are studying the nucleotide percentages of the genomes of two species of aquatic bacteria, species 1 lives in the arctic circle at temperatures near freezing and species 2 lives near hydrothermal vents at temperatures near boiling. Species 1 has a GC content of 39% Species 2 has a GC content of 62% 1a. What is the percentage of Adenine in each of the two species? (3) Sp 1 100-39=61/2=30.5 A sp 2 100-62=38/2=19 A 1b. What is the percentage of purine nucleotides in each of the two species? (3) Sp 1 50%, sp 2 50% A-30.5,G-19.5 A-19, G-31 1c. The pattern you noticed, that a species of bacteria that lives at extremely high temperatures has a higher GC content than other species, is very common. Why would you predict this pattern exists? (4) The higher G-C content is more heat stable due to the triple bonds present opposed to the two H bonds in A-T 2. You are studying two variants of the same protein which have the following sequences: Variant 1: Met Val Pro Gln Ala Trp Tyr Glu Variant 2: Met Val Pro Gln Ala Gly Tyr Glu 2a. What is the mRNA sequence for each of the variants? For any position in which more than one nucleotide is possible, use the designation “Pu” for any nucleotide that could be either Purine, “Py” for any nucleotide that could be either Pyrimidine, and “N” for any nucleotide that could be either a Purine or a Pyrimidine. Be sure to label the 5’ and 3’ ends.(4) 1: 5’-AUG-GUN-CCN-CAPu-GCN-UGG-UAPy-GAPu-3’ 2: 5’-AUG-GUN-CCN-CAPu-GCN-GGN-UAPy-GAPu-3’ 2b. What kind of mutation resulted in the difference between the protein variants? (2) Nonsynchronous transversion at 16th position from 5’ end 3. Describe in general the roles that replication, transcription and translation play in the production of a protein. (5) Replication does not participate in protein production. Transcription copies part of the dna sequence into a complementary rna strand. You get mrna which is the sequence of the gene, trna which translates nucleotide language into amino acid language and rrna which plays a structural catalytic role. Finally translation uses mrna to get amino acid sequence. 4. Fill in the appropriate blanks in the table below. Be sure to include the 5’ and 3’ labels for the mRNA and note the N and the C terminus of the protein as well. (10) DNA 3’ CGA TAC GAT GGN GCT ACT AGT 5’ DNA 5’ GCT ATG CTA CCN CGA TGA TCA 3’ mRNA 5’ GCU AUG CUA CCN CGA UGA UCA 3’ tRNA 3’ X UAC GAU GGN GCU X X 5’ Amino Acid N X MET LEU Pro ARG STOP X C 5. Describe the key experiments that showed that genes were composed of DNA. (8) Griffith studied streptococcus strains R and S. The R strain did not kill mice while the S strain did. When the s strain was denatured the mice lived but when R was added to denatured S the mice died. This indicated that a transformation factor was transferring from the S to change the phenotype of the R strain to make it lethal. Macarty, avery and mccleod also tested streptococcus. They removed lipids and polysaccharides, proteins, rna and dna one at a time. DNA was the only factor that when removed stopped the transformation, indicating that dna is the transformation factor. Hershey and chase used t2 bacteriophage to confirm genes were composed of dna. They labeled the phage with S (labels the protein) and P (labels the dna). They agitated the sample to separate the phage ghosts and phage infected bacteria. All of the P labeled infected bacteria was in the pellet while the S labeled protein remined in the supernate. This showed that dna entered the bacteria and was the hereditary molecule passed on by phage and inherited by progeny. 6. A friend of yours has been diagnosed with cancer in her kidneys. Her physician has told her that her cancer is the result of a somatic mutation that she recently acquired in a cell of her left kidney. She is concerned that her unborn child will be born with this same mutation since the physician tells her that the mutation likely occurred in her prior to the time she got pregnant. How would you explain her situation to her with regard to how much concern she should have about her child inheriting the mutation? (4) Somatic cells make other somatic cells which are not inherited by gametes. Germ cells make gametes so germ mutations would be passed down. Because friend has a somatic mutation there is no danger of the mutation being passed to her unborn child. 7. Describe the types of bonds that link nucleotides together in a DNA molecule, the relative strength of these bonds, and what role the differences in strength play in replication and transcription. (6) The nucleotides in a single strand are linked by covalent phosphodiester bonds which are much stronger than the hydrogen bonds that link the nucleotides across strands. The weaker double bonds make it easier for cells to break the stands apart and use the individual cells as a template 8. Describe in detail the process by which an E. coli cell makes a protein using a mRNA template. (10) *prokaryote, translation only bc mrna—if mentions dna then transcription and translation Initiation IF1 and IF3 bind mrna to 30 subunit of mrna. The position is determined by base pairing of rrna with the shine delgarno sequence in the 5’UTR which places the start codon in the P or peptidyl site. IF2 binds to a GTP and to fmet trna and attaches fmet trna to start codon. Hydrolysis of GTP provides energy for binding the large and small subunits. Elongation- repeats until the protein is made. EFTu binds to GTP providing energy for reaction, and also aminoacyl trna with anticodon in site A. EFTs- recharges EF-Tu, binds to EF-Tu and GTP to create EF-Tu-GTP. The ribozyme peptidyl transferase in 50s subunit catalyzes 2 reactions. The first cuts the amino acid from the P site and adds it to the A site. EF-G with GTP catalyzes the translocation of the ribosome by 1 codon in 5’