BIOL 101 1nd EditionExam # 2 Study Guide Lectures: 11 - 19Mitosis: How Cells Reproduce Class DiscussionI. ReproductionA. Asexual reproduction – creates offspring without the participation of sperm and egg; organism -> cell division -> entirely new organism 1. What cells use it? What organisms use it?Prokaryotes, some eukaryotes (yeast)2. Consequence-the parent and the offspring are genetically identical B. Sexual reproduction – requires fertilization of an egg by sperm. Resemble parents but are NOTgenetically identical.Come up with a list of actions or events that an animal cell must undergo to achieve division.Replicate all the organelles, DNA, and cytoplasm in the cell. The chromatin must coil up to form specific chromosomes. Chromosomes have to pair up. Nuclear envelope has to dissolve. Spindle must form and attach to the centromere of the chromosomes. The chromosomes line up on a the metaphase plate and then split and go to each pole, the cell pinches in and then creates two new cells. Growth factor must be there to keep cell division. Proteins are made. Interphase, Metaphase, Anaphase, Telophase, CytokinesisII. Eukaryotic Cell Cycle-(2 phases) A. Interphase (precedes both mitosis and meiosis) –3 subphases: 90% of the cell cycle. G1 Phase – Cell growth, proteins are produced, cytoplasm made, make more macromolecules, make new organelles, this is when the cell carries out its functionS Phase – DNA synthesis, chromosomes are duplicatedG2 Phase – Cell growth, proteins are produced, cytoplasm made, make more macromolecules, make new organelles, this is when the cell carries out its function the first line, the DNA replicates; The x is a chromosome that consists of two sister chromatids; the chromosomes divides into two separate ones Anatomy of chromosomes:-Chromosome = a double stranded DNA molecule-Sister chromatids = duplicated chromosomes that are connected, each chromatid will become a chromosome in the daughter cell.-Constricted region of a chromosome =__centromere_.-Protein complex that forms at the centromere to connect chromatids to microtubulespindle fibers = __kinetochore_._Histone_ = proteins that the DNA double helix winds around.__Heterochromatin__ = when DNA is tightly wound up.B. Mitosis. What cells in your body perform this? Somatic cells body cells (M)- 4 subphases: 1. interphase (DNA is being replicated and is being prepared to divide, the spindles are starting to from) 2. Prophase (the spindles continue to start forming and the DNA begins to pack tightly together) 3. ProMetaphase (nuclear envelope breaking apart, the spindles are attaching to the centromeres) 4. Metaphase (sister chromatids are lining up on the metaphase plate) 5. Anaphase (the sister chromatids are being pulled apart to the poles) 6. Telophase (cytoplasm is pinching off from each other and the two new cells are formed)In animal cells, you pinch the cell into two (cleavage furrow), but in plant cells a new cell wall is formed that divides the cell in two. PRACTICE: To the left is a picture of all the chromosomes of an animal cell in G1 of the cell cycle. Draw what this cell will look like at:1) G22) Metaphase3) After cytokinesisG2 Metaphase After cytokinesisIn G2 everything will be replicated. In metaphase the chromosomes will form and will split apart between the two poles. After cytokinesis, the the cell splits into two identical cells.III. CancerHow are cancer cells different from other cells? The control system is not in place and the cell keeps dividing. Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death.Benign – non cancerous, does not spread but can become malignant in some casesMalignant – cancerous, uncontrolled spread and growth of cellsMeiosisClass discussionI. Multicellular organisms like animals, plants, and ourselves inherit one set of chromosomes from each parent when a sperm fertilizes an egg. Meiosis, fertilization(zygote, mitosis)II. Meiosis is a type of cell division that produces haploid gametes in diploid organisms.i. Diploid organisms contain a set of __homologous chromosomes_____ in their____somatic cells_______.ii. The diploid number, or ___2n__, in humans = __46_.iii. Diploid organisms produce __haploid___ gametes.1. Examples: sperm, eggiv. The haploid number, or __n__, in humans =_23_.III. Meiosis reduces the chromosome number from diploid to haploid.i. Diploid or Haploid? diploid cellii. What would the haploid gametes of this cell look like? One cell would have the black chromosomes, one cell would have the white chromosomesiii. What is n=_3_?IV. In meiosis I HOMOLOGOUS CHROMOSOMES (don’t always have the same allele) separate. Illustrate meiosis I below.V. In meiosis II SISTER CHROMATIDS (duplicated chromosome, same allele) separate. Illustrate meiosis II below. Crossing over occurs in prophase one. The DNA does not get replicated the second time. Key differences between meiosis and mitosis Tetrads form during meiosis VI. Chromosomes orient independently at the metaphase platei. What does this mean and how do the equally probable arrangements of chromosomes contribute to genetic diversity?You never know which chromosomes going to be on which sideVII. Errors in meiosis lead to nondisjunction of the chromosomes.i. When nondisjunction occurs in meiosis I a pair of homologous fail to separate.ii. When nondisjuction occurs in meiosis II a pair of sister chromatids fail to separate.Directions:Cut out the chromosomes below. BRING TO S.I.!The chromosomes represent the chromosomes from a diploid cell. (Replicates are provided so you can have sister chromatid pairs. This is a cell in which 2n = 6. On a large clean surface use the chromosomes to illustrate the processes of meiosis (and mitosis) for yourself.With your cut-out chromosome you should be able to answer these questions:1. Do you need all the pieces above for both mitosis and meiosis?2. What are the major differences between mitosis and meiosis?3. When does crossing over occur?4. Why is 2n = 6? 5. Pick up two chromosomes that are homologs. Pick up two chromosomes that are sister chromatids. What is the difference in definitions between sister chromatids and homologs?6. Think about the idea of independent orientation at the metaphase I equator. How many different orientations are possible? For this concept, don’t think about crossing over). 7. Does independent orientation at