BIO 151 Exam 2 review Zehnder This review sheet will be graded for completeness meaning that you earn 5 points for submitting it on Moodle by Sunday night The answer key is already posted on Moodle so you can check your answers after you complete it This review does not cover everything that will be on the test and some things covered in this review may not be on the test ANSWERS ARE BOLDED 1 Categorize the following proteins as either being expressed from either proto oncogenes or tumor suppressor genes p53 Rb E2F cyclin CDK CDKI cell division receptor Proto oncogenes Cyclin CDK Cell division receptor E2F Tumor suppressor genes P53 Rb CDKI 2 Using the cell division diagram explain how a stem cell receiving a differentiation signal prevents the stem cell from self renewing A stem cell with a differentiation signal will bind to the differentiation receptor which will inhibit the cyclin cdk complex due to the expression of CDKIs The cell will also not move past the G1 S checkpoint 3 Human papillomavirus can cause cervical cancer The virus encodes E6 a protein that binds p53 What effect do you think E6 binding has on p53 activity A E6 activates p53 B E6 inactivates p53 causes rapid growth C E6 mutates p53 D E6 binding marks p53 for degradation 4 Explain your answer to 3 in one sentence The inactivation of p53 causes uncontrolled cell division due to the fact the p53 is a tumor suppressor gene 5 Describe the relationship between a genome chromosomes and genes A genome is the entirety of genes in a cell or organism Chromosomes are molecules of DNA that are packed together There can be many different genes on the same chromosome 6 Describe the general conditions that must be met at each of the three main cell cycle checkpoints G1 S cell has received division signal the DNA is intact the cell has grown enough cell has enough nutrients G2 DNA has fully replicated no DNA damage cell has grown properly M all chromosomes lined up correctly and are attached to microtubules 7 p53 can trigger apoptosis if certain cell cycle events fail How does this regulatory outcome benefit a multicellular organism This benefits a multicellular organism because it can stop a cell from having damaged DNA passed down through mitosis 8 Label one phosphodiester bond be sure to circle the entire bond the 3 end of the molecule the 5 end of the molecule Is this RNA or DNA 5 Two phosphodiester bonds are between the adenosine and cytosine and the cytosine and guanine 3 This is DNA 9 Imagine that you and your colleagues are working in a lab to develop a protein synthesis system for a new type of synthetic cell During your brainstorming sessions you propose that polycistronic mRNA would be much more useful than mRNA that is only translated into one protein because this would allow for multiple proteins necessary for a particular function to be translated together One of your colleagues says that is a good idea but if you decide to go with polycistronic mRNA then you need to make sure to use a prokaryotic translation system Why would it be a problem to use a eukaryotic translation system with polycistronic mRNA It would be a problem to use a eukaryotic translation with polycistronic mRNA because eukaryotic translations need to start with a 5 cap Without this the mRNA would not be able to be initiated It isn t a problem for prokaryotic cells however because they don t need to bind first to a 5 cap for the start codons to bind A prokaryotic ribosome that recognizes the Shine Dalgarno would be required 10 You are investigating an abnormal eukaryotic cell line that makes all of its mRNAs much longer than the mRNAs from normal cells that is they have more nucleotides than usual Intrigued you examine the proteins in these abnormal cells and note that many of them are either much longer or much shorter than the normal proteins from non mutant cells Assuming there is just one mutant defect in these cells what is that defect One possible defect is that the cells don t splice correctly It is possible that the spliceosomes aren t processing the primary transcripts properly and in turn the mRNA is longer As a result of this stop codons could be introduced prematurely or on the flip side the absence of splicing would result in longer proteins 11 Describe how a tRNA moves through the sites of a ribosome tRNA binds with the A site then is moved to the P site and then eventually to the E site as the ribosome shifts 12 Covalent bonds form during transcription and translation What type of covalent bonds forms during transcription Translation What do these covalent bonds link together With transcription phosphodiester bonds form between nucleotides in RNA In translation peptide bonds are formed between amino acids 13 During elongation of translation the growing polypeptide is transferred from the tRNA in the P site of the ribosome to the tRNA in the A site as a peptide bond is formed between the growing polypeptide and the newest tRNA 14 You re studying the MSC gene which is expressed only in mesenchymal stem cells which are multipotent adult stem cells found in multiple tissues including bone marrow and fat tissue Mesenchymal stem cells can self renew by dividing and can differentiate into multiple tissues including bone cartilage muscle and fat cells and connective tissue like ligaments and tendons You want to obtain samples of the MSC gene and mRNA for your experiments You have access to ligament cells embryonic stem cells and mesenchymal stem cells For each of the cells below indicate if you could get the MSC DNA mRNA both the DNA and mRNA or neither the DNA nor mRNA Ligament cells DNA Embryonic stem cells DNA Mesenchymal stem cells mRNA and DNA 15 Explain your answers to 14 in 1 2 sentences Since the cells all contain the same DNA the MSC gene is found in every cell which is why DNA is listed for all of them Since the gene is only expressed in the mesenchymal cells the mRNA is also present in those cells 16 Which of the following is are a critical region s of a tRNA molecule A amino acid attachment site and start codon B anticodon loop and ribosome binding site C stop codon and Shine Dalgarno sequence D amino acid attachment site and anticodon loop E ribosome binding site and 5 cap 17 Imagine that your lab is synthesizing a new type of cell One of your colleagues suggests that your synthetic cell should use prokaryotic systems for all the steps of gene expression transcription and translation because prokaryotic protein synthesis