1Unit II study guide Part A:Bio1. Describe a duplicated (or “replicated” ) Chromosome:a. In “G1” the new daughter cell is growing, and when it is faced with the decision to either chill out and perform regular cell activities or to divide.b. If the decision is made to divide the chromosomes replicate in the S phase of the cell cycle.i. It’s the synthesis of chromosomes.1. The DNA replicates in order to continue towards the dividing stages past interphase2. A Replicated chromosome has two sister chromatids joined at a centromere . (by cohesin proteins)3. Before replication there is no sister chromatid.2. To what does the cell cycle refer and what “event” (stages, steps, etc.) are involved?a. The eukaryotic cell cycle is a continuous process in which the life of the cell is carried out in 2 general main stages: Interphase and Mitotic phase.i. Interphase:1. Gap 1: cell grows and metabolizes, regulation of genes2. Synthesis: DNA synthesis in which chromosomes replicate.3. Gap 2: After DNA replicated, cell must synthesize proteins and structures to prepare for cell division.a. Replication of Centrosome (synthesize microtubules for spindle formation)i. Not in plant cells.ii. Mitotic Phase: 1. Mitois(nucleus divides)a. Prophase: Replicated chromosomes condense into distinct chromosomes(starting to, it looks like two spaghetti strands are stuck together)i. Centrosomes move to opposite polesii. Spindle microtubules lengtheniii. Nuclear membrane starts to dissolveiv. Nucleolus disintegrates.2b. Pro-metaphase: i. No mo’ nuclear membrane ii. Super distinct chromosomes.iii. Kinetochore at each centromere which completes the spindle apparatus. iv. Aster molecues: centrosome to cell edge.c. Metaphase:i. Spindle microtubules move chromosomes.ii. Chromosomes line up in a single file at the metaphase plate.1. 2 sister chromatids are facing the opposite poles so that each one goes to opposite sides during anaphase.d. Telophase:i. Spindle disassemblesii. Nuclear membrane reformsiii. Nucleolus reappearsiv. Mitosis is complete.2. Cytokinesis: cytoplasm dividesa. Cell membrane pinches in at the cleaveage furrow.b. Results into two daughter cellsc. Same chromosome number as each parent celld. IDENTICAL DNA AS PARENT!e. end of mitosis each daugther cell has the same number of chromosomes, but half the amount of cytoplasm.3. Why do cells/organisms need to regulate or control the cell cycle?a. To prevent/fix mutations and ensure the normal development of the cells and ultimately the organisms.b. Cell cycle is also controlled by regulatory proteins that act as signal molecules.4. 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.a. Checkpoints: pauses where a cell will assess itself, to see if everything is where it should be. Place where cell is regulated.b. There are molecular signals in the cytoplasm that regulate the cell cycle.c. Whether the cell cycle stops or keeps going through a checkpoint depends on what chemical signals are present.d. 3 major checkpoints: G1, G2, and M checkpoints:i. 1st: G1 (“restriction”)1. cell cycle pauses the cell while it’s chilling during G0 and the several things can happen depending on the signals:a. signals can direct the cell to pass the checkpoint and continue to “S”b. or signals can make the cell undergo apoptosis.ii. 2nd G2 checkpoint:1. if preparations for cell division are fine then signal molecules direct the cell to enter the “M” phase.2. Particular cell signal needed to pass the G2 Checkpoint is MPF; (it’s the complex generated from cyclin+Cdk)3. Clyclin: is the control may or may not be present, it’s facultative expressed (only when needed); fluctuates in concentration throughout the cell cycle.34. Cdk’s: ALWAYS AROUND IN THE CYTOPLASM.a. Bind to and activate cylins to get through a checkpoint.b. Genes that code for Cdk are always expressed.iii. Passage through the G2 check point:1. synthesis of G2 cylin fluctuates through the cell cycle: when [cyclin] increases (clyclin is expressed once it gets past S) it binds to its specific cdkMPF to proceed thorugh G2.2. Once it passes through the checkpoint : the cyclin part of MPF degrades but the cdk becomes available once again.iv. The MPF signal now puts the cell through the G2 checkpoint and initiates mitosis. 5. 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: a. General purpose of mitosis is to produce body cells, when they split it produces 2 identical cells with a complete set of DNA.i. The chromosome number is the same throughout mitotis except that during the S phase it becomes replicated and during the stages it condenses into clear sister chromatids but it means that it’s the same number of chromosomes.1. During anaphase, the chromatids move to opposite sides and each separated chromatid becomes a distinct chromosome. (so it kinda duplicates the number)2. At the end of mitotic division each of the daughter cells have the same number of chromosomes as the original parent cell. 6. 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?a. Cancer results when there are errors in control of the cell cycle.i. Possible errors in a cell-cycle stimulating pathway (POG mutation, excess in proteins.)= uncontrolled cell growth.ii. Errors in inhbiting pathway (TSG mutation) if P53 is missing transcription cannot be activated.1. Results in uncontrolled cell growth.iii. Mutations in growth factor signaling: 1. Cancer cells lose anchorage and density dependence.47. Compare/contrast somatic vs. germ cells (a.k.a. sex cells or gametes) with respect to location in an organism, function, how they are formed, and chromosome numbera. Somatic cells are body cells and are diploid.i. Contain 2 sets (2n) of chromosomes (maternal and paternal set)ii. Chromosomes exist in pair.b. Gametes (the egg and sperm cells) are haploid (n)i. Contain just one set of chromo, are not pairsii. It’s the individual n, before they come together when a new organism is formed and then it turns into diploid.8. . Describe a karyotype. What does a karyotype reveal? Why are karyotypes useful?a. it’s an organized display of chromosomes that shows the number and
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