MCB 150 FINAL EXAM
MCB 150 FINAL EXAM MCB 150
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This 16 page Study Guide was uploaded by Jessica Logner on Sunday May 8, 2016. The Study Guide belongs to MCB 150 at University of Illinois at Urbana-Champaign taught by Bradley G Mehrtens in Summer 2015. Since its upload, it has received 38 views. For similar materials see Molecular and Cellular Biology in Molecular, Cellular And Developmental Biology at University of Illinois at Urbana-Champaign.
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Date Created: 05/08/16
MCB 150 FINAL EXAM Chromosomal Domains/Territories organization of nuclei into discrete functional domains that play an important role in regulating gene expression and replication Interchomosomal Territory where DNA isnt Replicon unit of DNA synthesized from one ori SPhase replication of DNA Mphase condenses and separates DNA G1phase grows cell and synthesizes mRNA and proteins G2phase grows cell and synthesizes proteins Early Replication high gene density Late Replication low gene density Euchromatin less wound up chromatin that is more accessible. Early replication Heterochromatin more wound up chromatin that is less accessible. Late replication high gene density more likely to have all the genes needed, will be unwound sooner Proofreading 5' to 3' base adding, last base added is checked and if incorrect, removed 3' to 5' Hemimethylated one methylated strand and one nonmethylated strand. mismatch repair enzymes fix mitake in unmethylated strand MutS scans DNA looking for mismatched bases. Finds mismatch and latches on. If its not in the GATC sequence, it cannot tell parent from daughter MutH looks for hemimethylated DNA by looking for GATC sequence MutL links mutH and mutS together to communicate and loops out the region with mistake DNA polymerase III adds bases ligase fills in DNA poly III gap SOS repair faulty and leads to changes in DNA Point mutation point in genome where a change has been made. Includes base substitutions and framshift Base substitution Mutations the substitution of one base pair for another Transition type substitution Changes purine to purine or pyrimadine to pyrimadine Transversion base substitution purine to pyrimadine or pyrimadine to purine missense new codon sequence codes for different amino acid nonsense new codon sequence codes for stop same sense new codon sequence codes for same amino acid Insertion the insertion of hundreds of base pairs Deletion the deletion of hundreds of base pairs Framshift deletion of 1 or 2 base pairs that change the codon frame mutagen any agent that increases the number of mutations above background levels Specific repair systems target a single kind of lesion in DNA and repair only that damage Nonspecific repair system use a single mechanism to repair multiple kinds of lesions in DNA excision repair nonspecific repair where a damaged region is removed and replaced by DNA synthesis UvrABC complex binds to the damaged DNA then cleaves a single strand on either side of the damage, removing it point mutation a mutation that alters a single base triplet repeat expansion mutations a triplet sequence of DNA that is repeated and expanded in the dises allel chromosomal mutations changes in DNA that alter a chromosomes structure inversions a segment of chromosome is broken in 2, reversed and put back together translocation a piece of one chromosome is broken off and joined to another photorepair repairs thymine dimer caused by UV liht thymine dimer two adjacent and covalently linked thymines truncation to get a premature stop codon What three things can microtubules be used for? 1. Movement of materials/Guiding intracellular transport 2. Movement of sister chromatids/segregating chromosomes during mitosis 3. Propulsion or sweeping of fluids over membranes During what phase in the cell cycle is intracellular transport most likely to be seen? Interphase T/F Actin can have small vesicles moved along them if myosin is present True Most of the intercellular transport and traffic is handled through what cytoskeletal element? Microtubules T/F Microtubules form a web throughout the cell, including the plasma membrane False. They don't usually go all the way to the plasma membrane because it is covered by an actin network T/F The interphase microtubule array can be rearranged because it is not rigid True What happens to microtubules when there is a phase change from the G2 of interphase to M? Existing microtubules must depolymerize, wiping out the entire microtubule array. Then, new microtubules must be made from scratch because there needs to be a more specialized microtubule structure for mitosis T/F Microtubules help position organelles during interphase True What cytoskeletal element moves sister chromosomes to opposite sides of the cell during mitosis? The microtubule spindle fibers in the mitotic spindle T/F Each daughter cell gets half of the DNA because it is pulled apart during cytokinesis True How does cytokinesis occur? By the contraction of a belt of actin with the help of myosin T/F Chromosomes are pulled to opposite poles by actin filaments False. Microtubules What elements of a cell aid in propulsion and sweeping of fluids over membranes? Cilia, flagella, and basal bodies T/F Extensions of cytoplasm could be held in place with actin True Extensions to the cell can be created with what? Microtubules Cilia and flagella are made up of what? Microtubules What is the difference between microvilli and flagella/cilia? Microvilli are smaller and made out of actin while cilia/flagella are both made from microtubules T/F Cilia are stabilized extensions of cytoplasm True What purpose do cilia serve? Used by the epithelial cells lining the trachea to sweep foreign material out of the lungs. Basically it just moves liquid and mucous out What purpose do flagella serve? Swimming around in environments Flagella are usually ______ than cilia Longer, though they are structurally similar Microtubules are rigid/flexible and solid/hollow Rigid and hollow What are microtubules made up of? A protein called tubulin What molecules make up actin? GActin repeats T/F Tubulin is a dimeric protein made up of alpha and beta tubulin subunits True What is the largest difference between tubulin and Gactin? GActin: Gactin monomers in tandem repeats Tubulin: Alpha and beta tubulin subunits T/F In microtubules, the building block is a dimer of two polypeptide chains that are significantly larger than actin True T/F Alpha and beta tubulin subunits are similar in folding, interactions, and primary structure False. They have a slightly different amino acid primary structure T/F Tubulin dimers are added or removed from the end to grow or shorten microtubules True T/F The microtubules found in the cytoplasm during interphase or in the cell during Mphase are made exclusively from alpha and beta subunits True Both alpha and beta tubulin have a ________ binding site Nucleotide The nucleotide binding site in actin is for what? ATP The nucleotide binding side for alpha and beta tubulin is for what? GTP GTP has a high affinity for what? Other tubulins with GTP After dimer addition, the GTP in betatubulin does what? Is hydrolyzed to GDP What would happen if alpha tubulin's GTP was hydrolyzed? Then there would be no dimer formation because of the GTP affinity GDP has a high/low affinity for other tubulin Low Tubulin dimers are brought together and polymerize to form what? Microtubules How many protofilaments make up a microtubule? 13 How are microtubules assembled? Head to tail T/F Microtubules are not a continuous band of protein, but show an arrangements where all the head groups point one way and the tail groups point the other way True. This leads to microtubule polarity T/F Microtubules do not have polarity, rather they have an overall chemical charge False. Microtubules are polar and that polarity does not mean they have an overall chemical charge In vitro, polymerization and depolymerization occur at what end of the microtubule? Both Polymerization of a microtubule occurs faster at what end? The + end In vitro, which end allows faster polymerization? The + end, the end is a lot slower The outer diameter of a microtubule 25 nm The inner diameter of a microtubule 15 nm Thickness of one protofilament 8 nm T/F All of the dimers are arranged in the same orientation True In vivo, polymerization and depolymerization occur at what end of the microtubule? The + end only because the end is usually anchored into something and is occupied Why don't microtubules de/polymerize at the end in vivo? The end is occupied at that end and therefore cannot de/polymerize T/F In vivo, the beta tubulin ends all face towards the + end True GTPbound tubulin results in a high affinity for what? Other tubulin dimers What happens when GTPbound tubulin runs into another tubulin while its GTP is still bound? It will join up Shortly after tubulin binds to each other, what occurs? The GTP in the Btubulin subunit is hydrolyzed while the Atubulin subunit GTP remains unaffected What are the two possibilities of the Btubulin subunit after it is added to a MT? The Btubulin subunit will either fall off due to the hydrolysis of its GTP > GDP or its GTP will become trapped by something blocking it because if another dimer is added before hydrolysis occurs, the first becomes stuck T/F Lots of GTPbound tubulin means more addition and polymerization will be favored because more can be added before the GTP > GDP change has occured True Does microtubule polymerization/depolymerization use the GTP for anything? No. Its just about the conformational change of the tubulin. It enables rapid changes in the cytoskeleton If you are constantly adding the next ring to the growing microtubule, then you are doing what? Maintaining the GTP cap GTP Cap The ring of GTPbound tubulin that is found on the + ends of polymerizing microtubules MAPs Microtubule Associated Proteins Will there be a GTP cap if the outer ring of tubulin has dimers that have hydrolyzed their GTP? No Will there be a GTP cap if the outer ring of tubulin has dimers that have no hydrolyzed their GTP? Yes. If the end still has GTP on the Bsubunit, then that outer ring of dimers is called the GTP cap Is the GTP cap a separate structure? No If we have a ring of GTP caps, then it is likely what is occurring to a microtubule? That more dimers will keep being added, making more and more layers. It forms a flat later that wraps itself onto the end. The GTP cap moves forward one layer at a time No GTP Cap = GTP Cap = Depolymerization Polymerization What happens when the level of tubulin with GTP on it drops below the critical concentration? If no more GTPbound tubulin is added, then the ones on the end hydrolyze GTP to GDP. The molecules at the end of the MT can then unwind because the existing tubulin no longer wants to be there. As long as GTPbound tubulin is not supplied, then the end ones will float off and begin rapid depolymerization What happens to the GTP cap during MT catastrophe? The GTP cap will hydrolyze until it is all GDP and causes all the dimers to fall off Depolymerization of a MT will continue until what occurs? The cell either increases the GTPbound tubulin to let it start growing again or lowers the amount it needs and causes depolymerization What rephosphorylates the GDP in MTs? It actually takes out the GDP and puts in a fresh GTP. There is a swap Dynamic Instability The rapid switching between growth and shrinkage shown by microtubules due to the presence of GTPbound tubulin If a cell cannot enter or finish Mphase, what happens? Then you stop the cell from dividing or duplicating the DNA as seen in interphase T/F If you block the MT formation, then a cell will never finish mitosis True because MTs are used to separate the sister chromatids during Mphase, so if the MTs aren't working right, then Mphase is disrupted Clochicine and Colcemid Drugs that bind to tubulin dimers, therefore hiding all of the tubulin available to cells. This lowers the tubulin concentration to 0 and instantly induces depolymerization. They are not specific for which cells that they target, which makes them bad at treating cancer, since they affect all cells, including those that are needed for life and normal cellular functioning Vincristine and Vinblastine Drugs that bind to tubulin dimers, therefore hiding all of the tubulin available to cells. These drugs are specific to rapidly dividing cells and selectively inhibit them. They also effect cells that are supposed to be dividing naturally (causes chemo hair loss) Taxol Drug that is used to treat various cancers. Stabilizes MT formation and is opposite of other MT drugs mentioned before. Taxol binds to the end of MTs and keeps it there, stabilizing it. It also halts depolymerization, which causes the cell to remain in interphase because the microtubules cannot be depolymerized T/F Depolymerization of MTs causes cell structure to become more defined False. It causes loss of cell structure MTOC Microtubule Organizing Center What is the major MTOC in animal cells? The centrosome Where is the centrosome located in a cell? Adjacent to the nucleus, but not IN the nucleus T/F Microtubules are in the nucleus False. MTs will never get into the nucleus! T/F The () ends of MTs are anchored into the centrosome True Unless the MT is ________ from the anchor in the centrosome, the () end does not change in length Released T/F Centrosomes are made from a pair of centrioles True T/F The GTP is not hydrolyzed in the alphatubulin subunit of a tubulin dimer because it is inaccessible True The centrosome contains two structures called what? Centrioles Pericentriolar Material (PCM) Surrounds the centrioles and contains hundreds of ringshaped complexes composed of tubulin. The complexes are the organizing centers for the growth of the mitotic spindle How are centrioles orientated? 90 degrees from each other, perpendicular What is the structure of centrioles? They have a nine triplet arrangement and resemble a circle Nine Triplet Arrangement 9 triplets of microtubule. 27 microtubules in total. All are intact microtubules T/F The PCM has a very defined shape, just as the centrioles do False. The PCM does not have a defined shape. The PCM is an amorphous collection of proteins around the centrioles T/F The PCM is part of the centrosome True Where do microtubules emanate from? The PCM What is in centrosome? A pair of centrioles and the pericentriolar material Where do MTs actually come from? The PCM acts as the origin point for MTs. They do NOT come from the centrioles! If the centrioles are removed and only the PCM remains, what happens? The cell continues to make MTs w/o the centrioles, however, the efficiency of MT manufacture drops. This is either because centrioles may provide regulatory control or the cell has been damaged in the process of removing the centrioles Do centrioles have a defined role in the cell? No. Their exact role is unknown In a centrosome, which structures sere as nucleation sites for the formation of microtubules? YTubulin (Gamma). Also the reason why the () end of MT are not as likely to polymerize and acts as a platform at which MT grows from because dimers can easily attach T/F Microtubules originate in the centrosome, but not all microtubules stay anchored there True T/F The microtubules in nerve cells are all orientated the same way False. They are not. All MTs in nerve cells have the + end facing the synapse and the () end facing towards the cell body. They are not all orientated the same way due to the constant rearrangement and rewiring of nerve cell dynamics T/F The cell is capable of releasing the MTs and moving them after capping True. The cell makes MTs in the centrosome, chops them off at the trunk, caps both ends to prevent depolymerization/polymerization, then sends them elsewhere How are MTs released from the centrosome? By severing proteins, a type of MAP ABPs Actin binding proteins. Modulate the dynamics of the actin cytoskeleton, catalyze actin filament assembly or promote actin filament disassembly. Proteins that bind to actin filaments direct the location, rate, and timing of actin filament assembly and disassembly If you don't want a microtubule to be subject to polymerization or depolymerization, what can you do? Occupy both its + and end with capping proteins Neurons A nerve cell; the basic building block of the nervous system How many motor proteins work along microtubules? 2 T/F Myosins can recognize the dimers of tubulin in a microtubule and can walk along a microtubule if necessary False. They cannot recognize the dimers of tubulin in a MT and will not walk along it Kinesis and Dyneins move in the same manner as what other motor protein? Myosin Kinesin Move to the + end of a microtubule Dynein Move to the end of a microtubule Which of a microtubule motor protein contacts the cytoskeleton and which end is anchored into the object being moved? The head end contacts the cytoskeleton and does the moving while the tail end is anchored into the object being moved The binding of ATP to the dynein head group causes what? It to detach from the microtubule T/F Microtubule motor proteins are dimeric molecules, meaning that two proteins are intertwined to create it True What functions do microtubules and their associated motor proteins carry out? (5) Intracellular vesicle transport Organelle movement and positioning Color changes Bending of cilia and flagella Separation of sister chromatids and centrosomes during Mphase Why is it important to have dimers of proteins in the motor proteins of kinesin and dynein? Two head groups help keep it attached. The only thing keeping the motor protein on the MT is the head group. One of the "feet" is grounded while the other steps ahead T/F Vesicles that need to get towards the nucleus or centrosome would need to engage a dynein to move it towards the () end True T/F Vesicles that need to get away from the center of the cell engage kinesin True Why do vesicles not need to be particular about which MT they attach to when trying to transport throughout the cell? All the MTs look the same, it only matters where they go. The only thing that matters is the selection of the right MT to move the vesicle to the correct direction What happens if the vesicles get close to one another and are moving in opposite directions? will they collide? They will not collide, they will move to the side and allow the other to pass. They somehow shift their positions. The MT is big enough to let the motor protein and vesicle to shift positions to avoid collisions When speaking of MT motor proteins, in = what and out = what In = dynein () Out = kinesin (+) Cilia and flagella are identical/different in structure compared with eachother Identical Anoneme The functional unit of cilia and flagella in a 9+2 arrangement of microtubules. 9 pairs of MTs around a central pair in the middle unattached to each other T/F Cilia and Flagella are made up of 20 total intact protofilaments True Structure of an axoneme Surrounded by the plasma membrane. Contains MTs of defined length, capped to maintain length (no depolymerization or polymerization). 9 doublets consisting of an A tubule and a B tubule, where A contains 13 protofilaments and B is incomplete with 1011 protofilaments. Doublets are connected to eachother by stabilizing proteins called nexins. Doublets are connected to center channel with stabilizing proteins called radial spokes. The central pair are stabilized with more proteins that make up the inner channel. Dyneins then linked in to control movement. Inner pair are not attached directly to eachother. Basal Body A structure resembling a centriole that produces a cilium or flagellum and anchors this structure within the plasma membrane T/F Basal bodies and centrioles are identical under a microscope True What is the origin point for cilia and flagella? Basal bodies Structure of a basal body Made up of 9 triplets of microtubules, just like a centriole. In cross section, a basal body has 27 complete microtubules All of the ends of the MTs in a cilia or flagella are anchored into what? Basal body All of the + ends of the MTs in a cilia or flagella do what? Face out How do MT doublets move cilia/flagella? Dynein walking T/F Cilia move in a slow, regular pattern while flagella move in a whiplike pattern True
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