BSC2011 Exam #2 Study Guide1. Describe a duplicated (or “replicated”) chromosome.- Replicated Chromosome: 2 sister chromatids joined at a centromereoJoined by cohesin proteins2. To what does the cell cycle refer and what “events” (stages, steps, etc.) are involved?- Cell Cycle: The series of events that take place in a cell leading to its division and duplication (replication)oThe cell cycle creates new cells & allows cells to grow- Two parts:oCell growthoMitotic cell division3. Why do cells/organisms need to regulate or control the cell cycle?1BSC2011 Exam #2 Study Guide- Make sure that the cells are developing & functioning properly- Get rid of old, damaged, diseased, “malfunctioning” cells4. How do cells/organisms regulate or control the cell cycle? Explain the role of checkpoints. Explain the chemical control system that gets cells through the G2 checkpoint.- Cell cycle regulated by molecular signals in the cytoplasm & checkpoints- Three major checkpoints: G1, G2, and M checkpoints- The presence or absence of specific chemical signals determines whether a cell stops or proceeds through a checkpoint in the cell cycle- G1: Restriction CheckpointoSignals determine whether the cell…A) Pauses & enters G0, where the cell “hangs out” and does the jobit was intended to doB) Passes the G1 checkpoint and enters “S” (synthesis)C) Passes the G1 checkpoint and undergoes apoptosis (cell death)- G2 Checkpoint:oCell assess if preparations are “ok”oIf yes, signals direct the cell to enter “M” (mitotic phase)oMaturation Promoting Factor (MPF): A particular cyclin-Cdk complex needed to get through the G2 checkpointCyclin is gradually synthesized during S and G2Cyclin concentration high enough binds to & is activated by a particular Cdk protein complex now called MPFMPF signal moves the cell through the G2 checkpoint & into mitosisMPF NOT at G1 checkpoint- M Checkpoint:oCell assesses if mitosis proceeded successfullyoIf yes, signals direct the cell to enter cytokinesis (cell division)2BSC2011 Exam #2 Study Guide5. What is the general purpose of mitotic cell division? Describe the step-wise process of mitotic cell division. Compare the number of chromosomes before the start of mitosis, at each step, and at the end.- Mitosis: Cell division that preserves the parental number of chromosomes in the two daughter cellsoAsexual reproduction- General purpose of Mitosis: oCreate new cells quickly (replication)oGrowth & repairReplace worn-out or damaged cellsEnable multicellular organisms to growMitosis diploid (2n) diploid (2n)- InterphaseoG1Cell grows in size and synthesizes mRNA proteinsoSynthesis (S)Chromosomes (DNA) replicateCentrosomes replicateoG2Rapid cell growth & protein synthesis- ProphaseoCentrosomes move to opposite polesoSpindle microtubules start to lengthenoNuclear membrane begins to dissolveoNucleolus disintegratesoDNA begins to condense into distinct, replicated chromosomes- PrometaphaseoNuclear membrane is goneoChromosomes are clearly distinctoA kinetochore (kt) appears at each centromere3BSC2011 Exam #2 Study GuideoSpindle is completeoAster forms- MetaphaseoSpindle microtubules move the chromosomesoChromosomes line up single file along the midline/equator/metaphase plate- AnaphaseoCentromeres splitoSpindle microtubules pull apart sister chromatids toward opposite poles- Telophase & CytokinesisoSpindle disassemblesoNuclear membrane reformsoNucleolus reappears- Result of Mitosis:o2 diploid (2n) daughter cellsoSame number of chromosomes as parent celloIdentical DNA sequences as parent cell“Clones” of parent cell4BSC2011 Exam #2 Study Guide6. What do cancer and the cell cycle have to do with one another? What do cancer and gene regulation have to do with one another?- Cancer: A genetic disease caused by mutations to genes- Cancer-causing mutations usually involve tumor suppressing genes (TSGs), proto-oncogenes (POGs), and other genes that regulate the cell cycle- Ex) Normal tumor-suppressing genes (TSGs) restrict cell divisionoTSG mutation uninhibited cell growth cancer- Ex) Normal proto-oncogenes (POGs) stimulate cell divisionoPOG mutation overstimulated cell growth cancer7. Compare/contrast somatic vs. germ cells (aka. sex cells or gametes) with respect to location in an organism, function, how they are formed, and chromosome number.Gametes/Sex Cells/Germ Cells Somatic/Body CellsLocation in OrganismOvaries/testes Everywhere in the body except the ovaries/testesFunction Fertilization/sexual reproduction Many different types with 5BSC2011 Exam #2 Study Guidemany different functionsMethod of Formation Meiotic cell division Mitotic cell divisionChromosome # ½ the # of chromosomes for a given speciesHumans - 23 (haploid)Full # of chromosomes for agiven speciesHumans - 46 (diploid)8. Describe a karyotype. What does a karyotype reveal? Why are karyotypes useful?- Karyotype: An orderly display showing the number and types of chromosomes in a diploid cell arranged in homologous pairsoUses visible, condensed chromosomes from a cell undergoing mitosis- Karyotypes can be useful to detect:oAbnormal chromosome numberoAbnormal chromosome sizeoSex 9. What does it mean when we say that, in eukaryotes, “chromosomes exist in pairs?” What are the two chromosomes that make up a pair called? How are they similar to each other? How are they possibly different from each other?- In eukaryotes, chromosomes exist in pairs that are made up of one maternal and one paternal chromosome- The two chromosomes that make up a pair are called homologous chromosomes- Homologous chromosomes have the same:oLengthoCentromere positionoStaining patternoGenes for the same characteristics at corresponding loci- Homologous chromosomes can have different:oSequences of DNA within the chromosome6BSC2011 Exam #2 Study Guide10. Compare/contrast diploid chromosome number with haploid chromosome number. In what types of cells are these different numbers of chromosomes found?- Haploid (n): Having only one set of chromosomesoFound in gametes (sex cells)1 maternal set of chromosomes in an egg (n = 23)1 paternal set of chromosomes in a sperm (n = 23)- Diploid (2n): Having two sets of chromosomesoA maternal set & a paternal setoExist in pairsoFound in somatic (body) cellsEx) Human skin cell (2n=46)11. What is the general purpose of meiotic cell division? Describe the step-wise process of meiotic cell division. Compare the
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