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Chapter 5 Cancer DNA Synthesis, Mitosis, and Meiosis PowerPoint lecture prepared by Steve McCommas Southern Illinois State University Copyright © 2010 Pearson Education, Inc. What is Mitosis? Mitosis Takes one cell and produce two cells that are the genetic equivalent of the parent. Mitosis is nuclear division. It is the process by which a new cell receives the identical DNA as its parent cell The new cell is called the daughter cell. Mitosis produces two identical daughter cells Copyright © 2010 Pearson Education, Inc. How do you get to be 6 ft tall if you started out as a single cell? How do you heal a wound? How do you replace worn out cells? Copyright © 2010 Pearson Education, Inc. Why is mitosis important? This is how multicellular organisms grow, repair or heal injuries and maintain function. It is also how asexual reproduction takes place Copyright © 2010 Pearson Education, Inc. 5.1 What Is Cancer? Unregulated cell division (mitosis out of control) Tumor: mass of cells with no function Tumor Normal cell Normal cell division Copyright © 2010 Pearson Education, Inc. Potentially cancerous cell Unregulated cell division Malignant if tumor invades surrounding tissue (cancerous) Benign if tumor has no effect on surrounding tissue (noncancerous) Metastatic if individual cells break away and start a new tumor elsewhere (cancerous) Figure 5.2 5.1 What Is Cancer? Benign tumor: doesn’t affect surrounding tissues Malignant tumor: invades surrounding tissues; cancerous Metastasis: cells break away from a malignant tumor and start a new cancer at another location Tumor Normal cell Normal cell division Copyright © 2010 Pearson Education, Inc. Potentially cancerous cell Unregulated cell division Malignant if tumor invades surrounding tissue (cancerous) Benign if tumor has no effect on surrounding tissue (noncancerous) Metastatic if individual cells break away and start a new tumor elsewhere (cancerous) Figure 5.2 Fig. 12.17 Copyright © 2002 PearsonInc. Education, Copyright © 2010 Pearson Education, Inc., publishing as Benjamin Cummings 5.1 What Is Cancer? Metastatic cells can travel throughout the body via the circulatory system or the lymphatic system. Lymphatic system collects fluid that leaks from capillaries. Lymph nodes filter the lymph. Cancer cells found in lymph nodes indicate metastasis has taken place. Copyright © 2010 Pearson Education, Inc. 5.1 What Is Cancer? How are cancer cells different from normal cells? Cancer cells differ from normal cells: Divide when they shouldn’t Invade surrounding tissues Move to other locations in the body Copyright © 2010 Pearson Education, Inc. 5.1 What Is Cancer? Risk factors: increase a person’s risk of developing a disease Tobacco use: tobacco contains many carcinogens (chemicals that can cause cancer) Alcohol consumption: alcohol and tobacco increase risk in multiplicative manner High-fat, low-fiber diet Copyright © 2010 Pearson Education, Inc. 5.1 What Is Cancer? - Risk factors Lack of exercise increases risk in two ways Exercise keeps immune system healthy Exercise helps prevent obesity Increasing age Immune system declines with age Cumulative damage Cells that divide frequently Copyright © 2010 Pearson Education, Inc. 5.2 Passing Genes and Chromosomes to Daughter Cells Asexual reproduction: Only one parent Offspring are genetically identical to parent Sexual reproduction Gametes are combined from two parents Offspring are genetically different from one another and from the parents Copyright © 2010 Pearson Education, Inc. What must happen before mitosis? The cell must make exact copies of its chromosomes in the nucleus so each new daughter cell gets the same number and type of chromosomes as its parent cell A chromosome is a package of genes and it is made up of DNA. Copyright © 2010 Pearson Education, Inc. 5.2 Passing Genes and Chromosomes to Daughter Cells Before dividing, cells must copy their DNA Gene: section of DNA that has the instructions for making one protein One molecule of DNA is wrapped around proteins to form a chromosome containing hundreds of genes. Different species have different numbers of chromosomes (we have 46). What is a chromosome? What is a gene? What is our chromosome species number? Copyright © 2010 Pearson Education, Inc. 5.2 Passing Genes and Chromosomes to Daughter Cells Chromosomes are uncondensed before cell division. Duplicated chromosomes, held together at the centromere, are called sister chromatids They are duplicated through DNA replication A A b A b b Centromere Replication Sister chromatids Unduplicated chromosome Copyright © 2010 Pearson Education, Inc. C C C Duplicated chromosome Figure 5.6 chromosome (unduplicated) in a cell at interphase same chromosome (duplicated) in interphase prior to mitosis mitosis, cytoplasmic division chromosome (unduplicated) in a daughter cell at interphase Copyright © 2010 Pearson Education, Inc. chromosome (unduplicated) in a daughter cell at interphase Fig. 8.6, p. 131 Slide 4 What is DNA? DNA or deoxyribonucleic acid is a large molecule made of chains of repeating units called nucleotides. It contains the information for specifying the proteins that allow life in other words it contains instructions on how to make proteins Its structure was described for the first time in 1953 by James Watson and Francis Crick (won the Nobel prize for it) Copyright © 2010 Pearson Education, Inc. 5.2 Passing Genes and Chromosomes to Daughter Cells (a) DNA replication DNA molecule is split up the middle of the helix (enzymes do this) Nucleotides are added to each side (The enzyme is DNA polymerase) Result is two identical daughter molecules, each with one parental strand and one new strand. This is called semiconservative replication New strands Parental strands Copyright © 2010 Pearson Education, Inc. Figure 5.5a 5.2 Passing Genes and Chromosomes to Daughter Cells DNA polymerase: the enzyme that replicates DNA Forms covalent bonds between nucleotides on the new strands (b) The DNA polymerase enzyme facilitates replication. Unwound DNA helix DNA polymerase DNA polymerase Free nucleotides Copyright © 2010 Pearson Education, Inc. Figure 5.5b 5.2 Passing Genes and Chromosomes to Daughter Cells PLAY Animation—The Structure of DNA http://biologyinmotion.com/ Copyright © 2010 Pearson Education, Inc. Assignment Study all of Ch 5 on Cancer, DNA synthesis,Mitosis, Meiosis & The Cell Cycle. pp. 109-142. Assignment: Hand in at the beginning of next class (typed) the answers to questions 1-5 from the Savvy Reader (p.140). Do the online assignment for Ch 5 www.masteringbiology.com and submit to the grade tracker. We’ll have a test on Chapter 5__Wed June 9_____ *Remember that your service learning hours will be due shortly (room 1159) Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis Cell cycle: the “lifecycle” of the cell Three steps: Interphase: the DNA replicates Mitosis: the copied chromosomes are moved into daughter cells (division of the nucleus) Cytokinesis: the cell is split into 2 daughter cells. (This is when the cytoplasm divides) Copyright © 2010 Pearson Education, Inc. What is the cell cycle? The cell cycle is an ordered set of events, resulting in cell growth and division into two daughter cells The stages of the cell cycle during interphase are : G1 (stands for Gap1, growth takes place), S (stands for synthesis, this is when DNA is replicated) G2 (stands for Gap 2) Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis - Interphase Three phases: G1: cell grows, organelles duplicate S: DNA replicates G2: cell makes proteins needed to complete mitosis Most of the cell cycle is in interphase Copyright © 2010 Pearson Education, Inc. The Cell Cycle Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis - Mitosis Produces genetically-identical daughter cells Sister chromatids are pulled apart Four stages: (PMAT) Prophase Metaphase Anaphase Telophase Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis - Mitosis Prophase: Nuclear envelope disappears Thin chromatids condense into shorter and thick chromosomes Microtubules form a spindle (and pull the chromosomes toward the middle of the cell) Animal cells: microtubules attached to centrioles at the poles of the cell Metaphase: chromosomes are aligned across the middle of the cell Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis - Mitosis Anaphase: centromeres split, sister chromatids are pulled apart toward opposite poles by the microtubules in the spindle Telophase: Nuclear envelopes reform around chromosomes Chromosomes revert to uncondensed form Spindle dissapears Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis Suggested Media Enhancement: Mitosis To access this animation go to folder C_Animations_and_Video_Files and open the BioFlix folder. Also look at mitosis tutorial in www.cellsalive.com Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis - Cytokinesis Stage in which two daughter cells are formed from the original one Plants: New cell wall forms between the cells, built from cellulose Animals: Don’t have a cell wall Proteins pinch the original cell into two new cells After cytokinesis, cells reenter interphase. Copyright © 2010 Pearson Education, Inc. 5.3 The Cell Cycle and Mitosis PLAY Animation—Mitosis PLAY Animation—The Cell Cycle Copyright © 2010 Pearson Education, Inc. (4.5 min) Control System of the Cell Cycle The distinct events of the cell cycle are directed by a distinct cell cycle control system. These molecules trigger and coordinate key events in the cell cycle. The control cycle has a built-in clock, but it is also regulated by external adjustments and internal controls. Copyright © 2002 PearsonInc. Education, Copyright © 2010 Pearson Education, Inc., publishing as Benjamin Cummings Cell cycle control system There are three major checkpoints in the cell cycle. These are “stop and go” signals.(G1, M, and G2) It checks whether or not the cellular processes have been completed up to that point so it can proceed. The G1 check point is very important. Nerve cells and muscle cells switch into a non dividing stage called G0. They do not get a “go ahead” signal and stop dividing. Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation G1 checkpoint: are growth factors present? Cell must also be large enough and have enough nutrients G2 checkpoint: has DNA replicated properly? Metaphase checkpoint: have all chromosomes attached properly to microtubules? Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation Proto-oncogenes: genes that code for the cell cycle control proteins (control the cell cycle) Mutation: a change in the sequence of DNA This changes the structure and function of the protein Mutations may be inherited or caused by carcinogens What is a proto-oncogene? What is a mutation? What are some examples of carcinogens? Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation When proto-oncogenes mutate, they become oncogenes Their proteins no longer properly regulate cell division They usually overstimulate cell division (a) Mutations to proto-oncogenes Proto-oncogene Mutation Mutated proto-oncogene (oncogene) Mutation DNA Protein Copyright © 2010 Pearson Education, Inc. Functional protein stimulates cell division only when conditions are right. Mutated protein may overstimulate cell division by overriding checkpoint control. Figure 5.12a 5.4 Cell Cycle Control and Mutation Tumor suppressor genes: genes for proteins that stop cell division if conditions are not favorable When mutated, can allow cells to override checkpoints (b) Mutations to tumor-suppressor genes Tumor suppressor Mutation Mutated tumor suppressor Mutation DNA Protein Copyright © 2010 Pearson Education, Inc. Tumor-suppressor protein stops tumor formation by suppressing cell division. Mutated tumor -suppressor protein fails to stop tumor growth. Figure 5.12b Some examples of genes involved in cancer P53- this is a tumor suppressor gene. It orders the cell to self destruct if too damaged or tries to fix the damage. If p53 mutates and is not working damaged cells are allowed to divide. 50% of cancers are due to a mutated p53 gene that doesn’t work at the checkpoint. BRCA2 is a gene that makes a protein that repairs damaged DNA. A mutant version cannot help repair DNA and it will allow the cell to divide with the damage. Some Characteristics of Normal Cells 1. Normal cells exhibit contact inhibition 2.Normal cells exhibit anchorage dependency 3. Normal cells die after about 50 to 60 divisions Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation - Many Mutations Are Required for Cancer to Develop Progression from benign tumor to cancer requires many mutations. Angiogenesis: tumor gets its own blood supply Loss of contact inhibition: cells will now pile up on each other Loss of anchorage dependence: enables a cancer cell to move to another location Immortalized: cells no longer have a fixed number of cell divisions. What is a telomere? telomerase? Enzyme that prevents the degradation of the tips of chromosomes Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation - Many Mutations Are Required for Cancer to Develop Multiple hit model: process of cancer development requires multiple mutations Some mutations may be inherited (familial risk) Most are probably acquired during a person’s lifetime Copyright © 2010 Pearson Education, Inc. 5.5 Cancer Detection and Treatment Early detection increases odds of survival There are different detection methods for different cancers Some cancers produce increased amount of a characteristic protein Biopsy: surgical removal of cells or fluid for analysis Needle biopsy: removal is made using a needle Laparascope: surgical instrument with a light, camera, and small scalpel Copyright © 2010 Pearson Education, Inc. 5.5 Cancer Detection and Treatment Treatment Methods Chemotherapy: drugs that selectively kill dividing cells Combination of different drugs used (“cocktail”). Cells become resistant to the chemicals Interrupt cell division in different ways Helps prevent resistance to the drugs from arising Normal dividing cells are also killed (hair follicles, bone marrow, stomach lining) Copyright © 2010 Pearson Education, Inc. 5.5 Cancer Detection and Treatment Treatment Methods Radiation therapy: use of high-energy particles to destroy cancer cells Damages their DNA so they can’t continue to divide or grow Usually used on cancers close to the surface Typically performed after surgical removal of tumor What is the meaning of “remission” when talking about cancer? Copyright © 2010 Pearson Education, Inc. Reduction division to make sex cells or gametes Meiosis Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis What is meiosis? Specialized form of cell division in gonads to produce gametes Reduces number of chromosomes in each cell by one-half Chromosomes come in homologous pairs Gamete gets one of each pair Human somatic cells have 22 pairs of autosomes, and one pair of sex chromosomes Gametes are haploid; somatic cells are diploid Copyright © 2010 Pearson Education, Inc. What are homologous pairs of chromosomes? Humans have 46 chromosomes. 23 from the mother and 23 from the father. We get a complete set of genetic information from each parent. The chromosomes of these pairs that contain similar genetic material and similar size and shape are called homologous pairs of chromosomes. Copyright © 2010 Pearson Education, Inc. The chromosomes of a homologous pair Carry genes for the same characteristics at the same place, or locus Chromosomes Centromere Figure 8.12 Copyright © 2010 Pearson Education, Inc. Sister chromatids What is fertilization? What is a zygote? Fertilization is the union of two gametes, one from each parent. A zygote is a fertilized egg. It is diploid. Each gamete is haploid. During fertilization the diploid number is restored. Ex: in humans the egg and the sperm each contains 23 chromosomes so after fertilization the fertilized egg will have 46 chromosomes Copyright © 2010 Pearson Education, Inc. Terms to know Meiosis Gametes Diploid chromosome number Haploid chromosome number Zygote Homologous chromosomes Karyotype Non-disjunction Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis Egg cell has 23 chromosomes (unpaired). Egg-producing cells in the ovary have 46 chromosomes (23 pairs). Meiosis Sperm-producing cells in the testes have 46 chromosomes (23 pairs). Fertilization Meiosis Sperm cell has 23 chromosomes (unpaired). Diploid (2n) Copyright © 2010 Pearson Education, Inc. Haploid (n) Zygote has 46 chromosomes (23 homologous pairs). Diploid (2n) Figure 5.21 Meiosis: Two Divisions Two consecutive nuclear divisions Meiosis I Meiosis II DNA is NOT duplicated between divisions Four haploid nuclei are formed Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis Before meiosis, there is an interphase – DNA is duplicated Meiosis takes place in two stages: meiosis I and meiosis II End of previous mitotic event Cell growth and preparation for division G2 Interphase (G1, S, G2) Copyright © 2010 Pearson Education, Inc. Interphase and Meiosis S G1 Cell growth S and G phases similar to the S and G phases of mitosis DNA is copied Figure 5.22 5.6 Meiosis Meiosis I separates the members of a homologous pair from each other. During prophase I there may be crossing over between members of homologous pairs After meiosis I, the resulting cells are haploid Meiosis II is essentially like mitosis; it separates the sister chromatids Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis 4 Interphase and Meiosis (G1, S1, G2) 2 Meiosis I Meiosis II Prophase I Nuclear envelope starts to break down. Microtubules start to assemble. DNA condenses into chromosomes. Anaphase Homologous chromosomes are separated by shortening of microtubules. 4 Nuclear envelope Replicated uncondensed DNA Random alignments 2 Centrioles Crossing over may occur. 1 3 Microtubules Cell membrane Nucleus 3 1 G2 G1 DNA is replicated during S phase of interphase. Metaphase Homologous chromosomes align at middle of cell. S Copyright © 2010 Pearson Education, Inc. Figure 5.23 5.6 Meiosis Interphase and Meiosis (G1, S1, G2) Meiosis I 6 Prophase II Microtubules lengthen. Meiosis II 8 Anaphase II Sister chromatids are separated by shortening of microtubules. 8 6 5 7 9 5 Telophase I and Cytokinesis Cytokinesis results in two daughter cells. Nuclear envelopes reform. Copyright © 2010 Pearson Education, Inc. 7 Metaphase II Chromosomes align at middle of cell. 9 Telophase II and Cytokinesis Four haploid daughter cells result. Nuclear envelopes reform. Figure 5.23 5.6 Meiosis Crossing over: exchange of equivalent portions of chromosomes between members of a homologous pair Results in new types of gametes being formed Copyright © 2010 Pearson Education, Inc. Mitosis Meiosis COMPARED Occurs in somatic cells One duplication one division Result in two diploid (2N) daughter cells Daughter cells are identical to parent cell Copyright © 2010 Pearson Education, Inc. Occurs in gametes only One duplication two divisions Result in four haploid (N) daughter cells Daughter cells are different to parent cell. Introduces variety. 5.6 Meiosis (a) If crossing over does not occur in prophase I Red flowers Two types of gametes White flowers Meiosis Long grains Short grains (b) If crossing over does occur in prophase I Four types of gametes Meiosis Crossing over Copyright © 2010 Pearson Education, Inc. Figure 5.24 Crossing over Crossing over is the exchange of genetic material (DNA) between homologous chromosomes. During prophase I of meiosis, the homologous portions of two non-sister chromatids exchange places. They get so close to each other that chromosomes form connections and exchange sections of DNA Copyright © 2010 Pearson Education, Inc. Crossing Over •Each chromosome becomes zippered to its homologue •All four chromatids are closely aligned •Non-sister chromosomes exchange segments Copyright © 2010 Pearson Education, Inc. Why is crossing over important? It produces VARIETY in the offspring Check these meiosis tutorials: http://www.biology.arizona.edu/cell_bio/tut orials/meiosis/page3.html http://www.biologymad.com Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis Suggested Media Enhancement: Meiosis To access this animation go to folder C_Animations_and_Video_Files and open the BioFlix folder. Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis Random alignment: the way in which different pairs of chromosomes align and get separated during meiosis I is random Results in different types of games being formed Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis (a) One possible metaphase I alignment BRCA2 + HER2 + Two combinations of chromosomes in gametes BRCA2 + HER2 + BRCA2 + HER2 + 1/2 normal gametes Meiosis BRCA2 – HER2 – BRCA2 – HER2 – 1/2 gametes with two mutant alleles BRCA2 – HER2 – (b) Another possible metaphase I alignment BRCA2 + HER2 – BRCA2 + HER2 – BRCA2 + HER2 – Two additional combinations of chromosomes in gametes 1/2 gametes with HER2 mutation Meiosis BRCA2 – HER2 + BRCA2 – Copyright © 2010 Pearson Education, Inc. BRCA2 – HER2 + 1/2 gametes with BRCA2 mutation HER2 + Figure 5.25 5.6 Meiosis - Mistakes in Meiosis Nondisjunction: failure of homologues to separate normally during meiosis Results in a gamete having one too many chromosomes (trisomy) or one too few chromosomes (monosomy) Most embryos that result from such gametes will die before birth Several chromosome abnormalities are known in humans Copyright © 2010 Pearson Education, Inc. 5.6 Meiosis For cancer mutations to be passed on to offspring, they must take place in cells that give rise to gametes. Mutations in somatic cells (e.g., skin cancer) are not heritable. Copyright © 2010 Pearson Education, Inc. 5.4 Cell Cycle Control and Mutation Cell division is a tightly controlled process Normal cells halt at checkpoints Proteins survey the condition of the cell Cell must pass the survey to proceed with cell division What are proto-oncogenes? What are oncogenes? Copyright © 2010 Pearson Education, Inc. Karyotype and Alteration in Chromosome Number Copyright © 2010 Pearson Education, Inc. ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE What is a karyotype? A karyotype is a photograph of an individual’s chromosomes arranged in order A karyotype is a picture, a display of the 46 chromosomes. Shows 23 pairs of chromosomes, each pair with the same length, centromere position, and staining pattern. Copyright © 2010 Pearson Education, Inc. 5,000 Down syndrome is caused by trisomy 21 An extra copy of chromosome 21 Figure 8.20A Copyright © 2010 Pearson Education, Inc. Figure 8.20B One aneuploid condition, Down syndrome, is due to three copies of chromosome 21. It affects one in 700 children born in the United States. Although chromosome 21 is the smallest human chromosome, it severely alters an individual’s phenotype. Copyright © 2010 Pearson Education, Inc. The chance of having a Down syndrome child Goes up with maternal age Infants with Down syndrome (per 1,000 births) 90 80 70 60 50 40 30 20 10 0 20 Figure 8.20C Copyright © 2010 Pearson Education, Inc. 25 30 35 40 Age of mother 45 50 Sex chromosome pair Male pair is: XY Female pair is: XX How is sex determined? Copyright © 2010 Pearson Education, Inc. Klinefelter’s syndrome, an XXY male, occurs once in every 2000 live births. These individuals have male sex organs, but some are sterile. There may be feminine characteristics, but their intelligence is normal. Males with an extra Y chromosome (XYY) tend to somewhat taller than average. Trisomy X (XXX), which occurs once in every 2000 live births, produces healthy females. Monosomy X or Turner’s syndrome (X0), which occurs once in every 5000 births, produces phenotypic, but immature females. Copyright © 2010 Pearson Education, Inc. Review Questions 1. What is mitosis? What are the functions of mitosis? What type of cells undergo mitosis? 2.What is a pathologist? An oncologist? 3. What is cancer? What is a tumor? 4. What is the difference between malignant and benign tumors? 5.What is a metastasis? How does it happen? 6. What is a carcinogen? Name 3 known carcinogens. 7. List 4 risk factors for cancer and explain why. 8. What is the difference between sexual reproduction and asexual reproduction? 9.What is DNA? Who described DNA structure and when? What is a chromosome? What is a gene? What is our species number 10. What are sister chromatids? What is a centromere? 11. Describe what happens during DNA replication. Name an enzyme that facilitates DNA replication. 12.What are the complementary bases? What type of chemical bond joins them? Why is this bond advantageous in this case? 14. What is the cell cycle? What is included in interphase? What happens during the “S” part of the cycle? 15. What are the stages of mitosis? What must happen before mitosis starts? What are the most important things that happen in each? 16. Describe cytokinesis in animals. How is this different from cytokinesis is plants? 17. What are the “check points” in the cell cycle? What are some proteins that stimulate cells to divide? Copyright © 2010 Pearson Education, Inc. Review questions (continued….) 18.What is the function of growth factor proteins? 19. What is a mutation? What causes mutations? 20. What are proto-oncogenes? When do they become oncogenes? What do oncogenes do? Give an example of an oncogene. 21. What are tumor suppressors genes? 22. What is necessary for a malignant tumor to occur? What is the meaning of “multiple hit model” of cancer development? 23. Describe what is “contact inhibition” and “anchorage dependence” and explain what happens in cancerous cells. 24. How is cancer detected? What is a biopsy? A laparoscopy? 25. Describe the two common cancer treatments in use today. 26. What is meiosis? Where does it happen and what are the results of meiosis? 27.Define the following: gonads, gametes, somatic cells, autosomes, karyotype, zygote and homologous pairs of chromosomes. 28. What are alleles? What is the haploid number of chromososmes and what is the diploid number of chromosomes? Copyright © 2010 Pearson Education, Inc. Review questions (continued….) 29.What must happen before meiosis? What is crossing over? When does it happen? 30. What is the meaning of “random alignment”? When does it happen and why is it important. 31. What happens when there are mistakes in meiosis? In mitosis? What is non-disjunction? 32.What is the mane of a mistake that gives a person an extra chromosome? Give two examples? 33. Be able to compare mitosis and meiosis in terms of the number of daughter cells produced and chromosomes in the daughter cells. 34. What usually happens when there is an abnormal number of chromosomes? Why are sex abnormalities more common? Copyright © 2010 Pearson Education, Inc. Review questions 1. What is cancer 2. What is a carcinogen? Give examples. 3. List five risk factors for cancer and explain why these increase the chances of getting cancer. 4. What is the difference between a benign tumor and a malignant tumor? What is a metastasis? 5. What are the main differences between normal cells and cancer cells? 6. What must happen before cell division can take place? What do parent cells must pass on to daughter cells? 7. Where is DNA found? What is a chromosome? What is a gene? 8. What is DNA? Explain in general terms how DNA is replicated. Include the complementary bases and why it is called “semi conservative replication” 9. What is the cell cycle? What are the stages of the cell cycle and what happens in each? 10. What are some factors known to control the cell cycle? What is the G0 stage and what cells go into it? 11. What is mitosis. List the stages of mitosis in order and explain the main events that happen during each one. What is cytokynesis? 12. What is the end result of mitosis? What is the result of mitosis? 13.What is the function of mitosis compared to the function of meiosis? 14. What is meiosis? What are homologous chromosomes? What is crossing over? 15.Discuss the main differences between mitosis and meiosis. Copyright © 2010 Pearson Education, Inc. More Review Questions 1. What is a somatic cell? An autosome? 2. Free radicals remove ______ from other molecules. 3.What is the name of a replicated chromosome? What is the name of the place where the two halves of a duplicated chromosome are connected? 4.Which word describes a cancerous tumor? 5.List the events of the cell cycle in order.___,___,___,___,___. Which part of this is interphase? 6.If 25% of the bases of its DNA of one species are G. What percent would be C? 7.What are gametes? How many chromosomes gametes have compared to somatic cells? What is haploid? Where do you find the Diploid chromosome number? 8.What are homologous chromosomes? 9.The gene that makes a protein that checks for mistakes at a checkpoint in the life cycle of a cell is _______ gene. 10.A gene that controls the cell cycle of a cell is called a/an _______ gene. 11.What is likely to happen if the p53 gene is damaged is mutated? 12.What is the meaning of the “multiple hit” model of cancer? 13.What is a biopsy? 14.What is the result of radiation therapy? 15.What is chemotherapy? 16. What is CA125 test? Why is it not practical to do routine tests for CA125? 17. What is the name of the process by which tumors attract blood vessels to create their own blood supply? 18. What is the name given to genes that are in the same chromosome? 19. During which part of meiosis crossing over occurs? Why is crossing over important? 20. List two types of inhibitions that are lost in cancer cells. Copyright © 2010 Pearson Education, Inc.