Exam 4 Review Questions 1 A Draw the lac operon in an E coli chromosome and label the following parts lacZ lacY lacA lacI operator promoter operon B What are the protein products of lacI lacZ and lacY and their function in the cell lacI repressor binds operon at the operator sequence to block transcription lacZ B galactosidase cleaves lactose to glucose and galactose lacY galactoside permease protein for membrane transport of lactose 2 How are CAP protein and cAMP involved in positive control of lac operon CAP complex forms and binds DNA at CAP site allowing RNApoly to bind more tightly and have more frequent transcription 3 Explain how expression of the lac operon is regulated by the following a Repressor blocks transcription by binding to operon at operator sequence b Lactose inducer binds the repressor causing a conformation change in repressor repressors falls off and transcription proceeds c Glucose regulates cAMP site low glu high cAMP cAMP CAP complex forms and binds DNA at CAP site to allow RNApoly to bind tighter 4 Which proteins molecules are examples of positive control Negative control Which is responsible for feedback inhibition positive lactose negative repressor feedback glucose bc catabolite repression catabolite comes back and decreases trancription 5 Fill out this chart about lac operon regulation When glucose levels are HIGH HIGH LOW cAMP levels are HIGH LOW low high high Lactose levels are LOW HIGH high Because the repressor is ON OFF on off off 6 Explain how presence or absence of cAMP affects how RNA polymerase interacts with the promoter region of the lac operon 7 Fill in the table describing methods to control eukaryotic gene expression Type of Gene regulation Chromatin remodeling Describe the mechanism Where does it take place DNA is highly condensed wraps around histones to form nucleosome fiber chromatin protein scaffold control HATS adds acetyl groups to histone decondenses bc DNA is charged control HDACs removes acetyl to make it more condenses nucleus Transcription Differential gene expression regulatory transcription factors enhancers more than 100KB away from promoter silencers promoter proximal elements basal transcription factors promoters TATA binding proteins nucleus mRNA nucleus Alternative splicing DNA can yield more than one mRNA transcript Processing posttranscriptional control mRNA stability mRNA nucleus RNApoly small hairpin miRNA RISC siRNA binds target mRNA cut Cyto Translation Regulatory proteins Cyto Post translational modification Chaperone proteins phosphorylation ubiquination target protein for destruction cyto 8 Why is post translational regulation considered a process of gene expression control that is speedy at the expense of efficiency Give an example of post translational control Transcription RNA processing translation used up energy and materials it is wasteful to produce proteins that won t be used Examples protein folding enzyme modification phosphorylation 9 What is the difference between regulatory and basal transcription factors regulatory binds enhancers silencers that can be very far away from the promoter basal binds promoters such as TATA binding proteins that are very close to promoters 10 What is the process for RNA interference RNAi RNApoly transcribes small RNA hairpin miRNA is formed by initial processing trimmed from transcript Hairpin cut to form mature duplex 2 small strands miRNA associates with RNA induced silencing complex RISC now called siRNA siRNA complementary binds to target mRNA Then enzyme inside RISC cuts mRNA 11 Name and number the events of mitosis in order Number 3 Name of stage 5 Metaphase Telophase 1 Prophase 2 Prometaphase 4 anaphase Description Chromosomes complete migration to middle of cell Nuclear envelope reforms and spindle apparatus disappears Chromosomes condense and spindle apparatus begins to form Nuclear envelope breaks down Kinetochore microtubules contact chromosomes Sister chromatids separate and chromosomes are pulled to opposite poles of the cell 12 Diagram mitosis for 4 chromosomes describe each phase and describe the resultant daughter cell 13 How do chromosomes move during mitosis Kinetochore microtubules shorten during anaphase due to loss of tubulin dimers at the kinetochore As they shorten motor proteins walk the chromosome down the remaining length of the kinetochore MTs 14 Differences between Mitosis and Meiosis Feature of Cell Divisions Mitosis 1 Meiosis 2 of chromosomes in daughter cells compared with parent Synapsis of homologs same half no yes of Crossing over events none Makeup of chromosomes in daughter cells Role in organism life cycle same 1 or more per pair of homologs Different due to recomb Asexual reproduction growth Sexual reproduction 1 Match the following checkpoint to its phase in the Cell Cycle can be more than 1 a G2 checkpoint b Metaphase checkpoint c G1 checkpoint b All chromosomes are attached to spindle apparatus a c DNA is undamaged a Chromosomes have successfully replicated c Nutrients and cell size is sufficient a Activated MPF is present 2 Diagram meiosis
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