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MITOSIS AND MEIOSIS FURTHER ANALYSIS Name: Mitosis Questions 1. What is the overall purpose of mitosis? To produce more identical somatic cells. 2. Give examples of why an organism might need to be able to produce more cells. Growth of an organism. To heal injuries. To prevent the cell from becoming too large. In the space provided, write the letter of the description that best matches each term. 3. E__ First gap (G1) phase A. division of the nucleus 4. D__ Synthesis (S) phase B. cytoplasm divides and daughter cells become physically separated 5. C__ Second gap (G2) phase C. final preparations are made for the cell to divide 6. A__ Mitosis D. DNA is copied 7. B__ Cytokinesis E. cell grows and carries out its routine functions 8. What function do spindle fibers perform during mitosis? They attach to chromosomes, moving them to the middle (metaphase) and then pulling them apart (anaphase) 9. What function do centrioles perform during mitosis? They produce spindle fibers. In the space provided, write the letter of the description that best matches each term. 10. __C__ Prophase 11. __B__ Telophase 12. __A__ Metaphase 13. __D__ Anaphase a. Chromosomes align in center of cell. b. Nuclei reform. Chromosomes unwind. Spindle fibers break down. c. Chromatin condenses into chromosomes. Nucleus disappears. d. Chromatids are pulled by spindle fibers to opposite poles of the cell. Complete each statement by circling or highlighting the correct term or phrase in the brackets. 14. Cytokinesis takes place [ prior to / following ] mitosis. 15. During cytokinesis in animal cells, a cleavage furrow is formed by [ a cell wall / a belt of proteins ]. 16. In plant cells, a new cell wall is formed by [ vesicles / cell plates ] holding cell wall materials. 17. Following cytokinesis, the new daughter cells enter the [ G1 / G2 ] phase of [ prophase / interphase ]. 18. Mitosis results in [ two / four ] daughter cells which are genetically [ identical to / different from ] the parent. 19. In the space below, draw a chromosome and label the following terms: chromosome, chromatid, centromere. Chromatid x Chromatid Centromere Chromosome Meiosis Questions In the space provided, write the name of the stage of the Meiosis cell cycle that is being described. 1. Anaphase II The chromosomes divide, and the chromatids move to opposite poles of the cell. 2. Interphase Takes place prior to meiosis I, DNA is duplicated. 3. Telophase II Nuclei reform in all four daughter cells. Chromosomes unwind back into chromatin. 4. Anaphase I The homologous chromosomes separate. Full chromosomes are pulled to the poles. 5. Prophase I Chromosomes form. Homologous chromosomes pair up and crossing over occurs. 6. Prophase II Both nuclei disappear and chromosomes condense in each cell. 7. Cytokinesis Takes place following meiosis II. Results in four sperm or one mature egg cell. 8. Metaphase II Chromosomes line up single file along the middle of each cell. 9. Telophase I Two nuclei reform. Results in two haploid daughter cells. 10. Metaphase I Homologous chromosome pairs attach to spindle fibers and align in the middle of the cell. Complete each statement by circling or highlighting the correct term or phrase in the brackets. 11. The purpose of meiosis is to produce [ diploid / haploid ] [ somatic / gamete ] cells. 12. In the production of sex cells, DNA is duplicated [ once / twice ] and the cell divides [ once / twice ]. 13. The pairing up and crossing over of homologous chromosomes takes place in [ interphase / prophase I ]. 14. In metaphase I of meiosis, chromosomes line up [ in homologous pairs / single file ]. 15. Meiosis results in [ two / four ] daughter cells which are genetically [ identical to / different from ] the parent. 16. How are metaphase I and metaphase II of meiosis different from one another? In metaphase I, chromosomes line up in homologous PAIRS. In metaphase II, chromosomes line up single file. 17. How are anaphase I and anaphase II of meiosis different from one another? In anaphase I, full chromosomes are being pulled to the poles. In anaphase II, chromatids are being pulled to the poles. 18. Describe crossing over. How does crossing over benefit an organism? Crossing over is an exchange of genetic information which takes place in Prophase I. Crossing over produces genetic variation. 19. Compare and contrast spermatogenesis and oogenesis. Spermatogenesis is the production of sperm, oogenesis is the production of eggs. Both sperm and eggs are haploid gametes. In spermatogenesis, four mature sperm are produced in the testes. In oogenesis, four cells are produced in the ovaries but only one matures into an actual egg cell. Mitosis vs. Meiosis Questions Fill in following tables for Mitosis and Meiosis… MITOSIS MEIOSIS Purpose of process To produce somatic cells. Diploid Diploid To produce gametes (sex cells). Diploid Haploid Type of parent cell (haploid or diploid) Diploid Diploid Chromosomes of parent cell (haploid or diploid) Same as above Same as above Type of daughter cell (somatic or gamete) Somatic Gamete Chromosomes of daughter cells (haploid or diploid) Diploid Haploid Number of daughter cells following the complete process 2 4 Number of times DNA replicates prior to cell division 1 1 1 2 Number of times nucleus divides EVENT MITOSIS MEIOSIS I MEIOSIS II Does crossing over occur? (yes or no) No Yes no How do chromosomes line up in the middle during metaphase? Single file In homologous pairs Single file What separates in anaphase? Chromatids Full chromosomes Chromatids Do homologous chromosomes pair up in prophase? No Yes no No Yes yes Is genetic variation produced? Application Questions 1. Explain the connection between mitosis and cancer. How does your body try to prevent cancer from forming? Cancer results when cells no longer receive the signal to stop dividing. In other words, cancer is uncontrolled mitosis. Apoptosis (programmed cell death) is one way your body prevents cancer from forming. 2. The diploid cell of a polar bear has 74 chromosomes. a. Following mitosis… 74 ___ 74 74 ___ b. Following meiosis… Following fertilization…. 37 ___ 37 ___ 74 37 ___ 37 ___ 37 ___ 74 37 ___ 3. The **starred** cell in the question above represents a zygote, or fertilized egg. a. This is also known as the first _________somatic___________ cell. b. This cell will now begin to undergo which process in order to develop into a baby? Mitosis 4. An error during mitosis cannot be passed on to future generations. An error during meiosis, however, CAN be passed on to future generations of offspring. Defend the truth of this statement. Mitosis is the reproduction of somatic cells. If an error occurs, it doesn’t matter because somatic cells aren’t passed on from parent to offspring. Meiosis is the production of gametes, or sex cells. Sex cells are what become people. Therefore, if an error occurs in meiosis it will be given to the baby when the egg is fertilized. 5. Down Syndrome is a genetic disorder that results when a person’s cells have an extra 21st chromosome (instead of the normal two 21st chromosomes, there are three). Explain the connection between Down Syndrome and meiosis. When eggs and sperm are produced following meiosis, they should each end up with one 21st chromosome. That way the cell has two when the egg is fertilized. If an egg or a sperm somehow ends up with two 21st chromosomes, there will be a total of three 21st chromosomes when the egg is fertilized. The fertilized egg with three 21st chromosomes will then begin going through mitosis and every single new cell will also have three 21st chromosomes.