PLEASE NOTE: please also refer to and be able to work problems on theseparately posted Study Guide Part B and C entitled “Practice Mitosis/MeiosisProblems” and “Practice Mendelian Inheritance Problems”, respectively.The purpose of this study guide is to “encourage” you to review your notes, text material, and outsidesources and to integrate numerous facts and terms into broad but meaningful concepts. Please try andwork on your own at first, but don’t hesitate to ask for assistance from either me or your TAs. We willrandomly select a question (or part thereof) to use on your Unit II exam. – Dr. SpearsUNIT II: Patterns of Inheritance (Mendelian genetics; also cell division and cell cycle)1. Describe a duplicated (or “replicated”) chromosome.o Shaped like a X o 2 sister chromatids joined at a centromere; joined by cohesion proteins 2. To what does the cell cycle refer and what “events” (stages, steps, etc.) are involved?o The cell cycle Two components: Cell growth and mitotic cell division Mitosis= division of the nucleous that preserve the parental chromosome number in both daughter cells Continuous process 1. Two new daughter cells are created2. In G1 a new cell grows3. Decision is made to just hang out performing cell activities or to divide or not (die)4. If dicision is made to divide then chromosome replicate in S5. In G2 the cell prepares to divide6. In M the cell divides by mitosis and cytokinesis into 2 daughter cells (each with the original number of chromosomes) Two general phases Interphase: 3 Stages- G1(gap)o Cell is growing, metabolizing. Genes are being regulated- S (Synthesis)o DNA synthesis, chromosome replicate- G2 (gap)o After DNA replicated, cell must synthesize proteins and structures to prepare for cell division. o Centrosome replicates This is microtubule organzing center Each centros consists of a pair of cylindrical centrioles. These contain microtubules needed for spindle formation (absent in plant cells) Mitotic phase: 2 components- Mitosis: division of nucleus- Cytokinesis: Division of cytoplasm 3. Why do cells/organisms need to regulate or control the cell cycle?o If you don’t control cell division, you get mass of cells 4. How do cells/organisms regulate or control the cell cycle? Explain the role of checkpoints. Explain thechemical control system that gets cells through the G2 checkpoint.o Molecular signals In cytoplasm Regulate cell cycle Whether cell cycle stops or proceeds through a checkpoint depends on what chemical signals are presento Cell cycle is regulated at various checkpoints 3 major checkpoints inbetween varius stages: G1 G2 M G1 Restriction checkpoint Cell cycle pauses (just doing its job in G0) if directed to do so by signals, or other signals direct the cell to pass the checkpoint it enters S or even to undergo apoptosis if defective Basically decides if cell hangs out, divids, or commits sucide G2 checkpoint Signals assess preperations and if “ok” direct cell to enter M Mitotic phase5. What is the general purpose of mitotic cell division? Describe the step-wise process of mitotic celldivision. Compare the number of chromosomes before the start of mitosis, at each step, and at the end.o Pupose: preserve the parental chromosome number in both daughter cells. Make daughter cells identical to parento Step-wise Process1. Prophase Centrosomes move to opposite poles Spindle starts to form Nuclear membrane envelope starts to dissolve Nucleolus disintegrates Chromatin that replicated during S begin to condense into distinct chromosomes2. Pro-Metaphase Nuclear membrane now disassembled Chromosomes clearly distinct A kinetochore appears at each centromere- Complex of proteins attached to the centromere that attaches sister chromatids to the spindle fibers Spindle apparatus complete3. Metaphase Middle of cell Spindle microtubules move chromosomes Chromosomes line up single file at the midline or cell equator (metaphase plate)- The two sister chromatids of a replicated chromosome face opposite poles4. Anaphase Apart Centromere splits Spindle microtubules pull apart sister chromatids toward opposite poles- Tubulin subunits of a microtubule break down- Each separated chromatid is now called a distinct chromosome- As soon as they get pulled apart you have double the amount5. Telophase Spindle disassembles Nuclear membrane reforms Nucleolus reappears Mitosis or Nuclear division is now complete Cytokinesis- Cell membrane pinches in (invaginates) at cleavage furrow- Cytoplasmic division now complete- 2 daughter cells resulto Same chromosome # as parent cello Identical DNA as parent cell 6. What do cancer and the cell cycle have to do with one another? What do cancer and gene regulationhave to do with one another?7. Compare/contrast somatic vs. germ cells (a.k.a. sex cells or gametes) with respect to location in anorganism, function, how they are formed, and chromosome number.8. Describe a karyotype. What does a karyotype reveal? Why are karyotypes useful?o Karyotype An orderly way of displaying the number and types of chromosomes in a cell; displays visable condensed already replicated chromosome undergoing mitosis The two chromosomes in a pair are said to be homologous Each have the same number and kind of genes Useful to: See if individual has right number of chromosomes To determine gender Detect abnormalities in chromosome number, size etc.9. What does it mean when we say that, in eukaryotes, “chromosomes exist in pairs?” What are the twochromosomes that make up a pair called? How are they similar to each other? How are they possiblydifferent from each other?o Chromosomes exist in pairs (in somatic cells) In somatic cells, chromosomes exist in homologous pair Have same number and kind of genes Contain maternal and paternal set Can have different Alleles Different versions of the same kind of genes that code for a similar kind of protein but can have a different DNA sequence Alleles can be same or different on pair of homologous chromosomes 10. Compare/contrast diploid chromosome number with haploid chromosome number. In what types ofcells are these different numbers of chromosomes found? (I know…this is similar/related to question 7!)o Diploid 2n Found in somatic cells: body cells- muscle, nerve, skin etc Maternal and paternal seto
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