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CELL REPRODUCTION SB1. Students will analyze the nature of relationships between structures and functions in living things a. Explain the role of cell organelles for both prokaryotic and eukaryotic cell in cell reproduction LEQ: What are the four main stages of the Cell Cycle? Cell Reproduction Each organism has a specific number of chromosomes Made of DNA store/transfer genetic info If the chromosome number is not maintained from generation to generation, mutations may evolve. Humans have 46 chromosomes Cell Reproduction Two types of cell division maintain chromosome number from generation to generation: Mitosis Meiosis MITOSIS Process by which a cell divides its nucleus and contents Produces identical diploid cells Cell that contains two copies of each chromosome, one from mother and one from father. Occurs in somatic (body) cells Cell Reproduction Cell Cycle Gap 1 (G1) DNA Synthesis (S) Gap 2 (G2) Mitosis (M) INTERPHASE The cell cycle is a regular pattern of growth, DNA replication, and cell division The cell cycle has four main stages The Cell Cycle 4 Stages Main Stages: Gap1 (G1) DNA synthesis (S) Copies DNA Gap2 (G2) Cell growth & normal functions Additional growth, DNA checkpoint Mitosis (M) Includes division of cell nucleus (mitosis) and division of cytoplasm (cytokinesis) Only occurs if the cell is large enough and the DNA is undamaged. The Cell Cycle Parent cell centrioles spindle fibers centrosome nucleus with DNA Interphase prepares the cell to divide (G1, S, G2) During interphase, the DNA is duplicated. Interphase is followed by Mitosis and cytokinesis (M) Mitosis and cytokinesis produce two genetically identical daughter cells. The Cell Cycle Mitosis (M) Mitosis divides the cell’s nucleus in four phases: Prophase Metaphase Anaphase Telophase The Cell Cycle Phases of Mitosis During Prophase, chromosome condense, nuclear membrane begins to disappear and spindle fibers form. Centrioles Spindle fibers The Cell Cycle Phases of Mitosis During Metaphase, chromosomes line up in the middle of the cell. Metaphase Plate The Cell Cycle Phases of Mitosis During Anaphase, sister chromatids separate to opposite sides of the cell. The Cell Cycle Phases of Mitosis (M) During Telophase, the new nuclei form and chromosomes begin to uncoil. Cleavage Furrow The Cell Cycle Cytokinesis Cytokinesis differs in animal and plant cells Division of cytoplasm In animal cells, the membrane pinches closed (forms a cleavage furrow) In plant cells, a cell plate forms to separate cells. The Cell Cycle Cytokinesis Animal Cell Cleavage Furrow Plant Cell Cell Plate MEIOSIS Process that divides a diploid cell into haploid cells Important in forming gametes for sexual reproduction Cell that only has one set of chromosomes Sex cells (egg or sperm cell) Occurs in sex cells of reproductive organs Process of Meiosis During Meiosis, diploid cells undergo two cell divisions that result in four haploid cells Role of Meiosis: Reduces chromosome number Increases genetic diversity Process of Meiosis Cell go through two rounds of division Meiosis I Meiosis II Each have four phases similar to mitosis Process of Meiosis Meiosis I Occurs after DNA has been replicated Divides homologous chromosomes in 4 phases. Homologous chromosomes are similar but not identical. homologous chromosomes - Code for same traits Prophase Metaphase MOM DAD Anaphase Telophase Process of Meiosis Meiosis II Divides sister chromatids in four phases. Sister chromatids are copies of the same chromosome. DNA is not replicated between meiosis I and II. Prophase II Metaphase II sister chromatids Anaphase II Telophase II Process of Meiosis Haploid cells created by meiosis develop into mature gametes. Gametogenesis is the production of gametes. Differs between females and males Process of Meiosis Sperm become streamlined and motile Sperm primarily contribute DNA to embryo The egg gets most of the contents; the other cells form polar bodies Egg contributes DNA, cytoplasm, & organelles to embryo Mitosis vs. Meiosis Similar to mitosis, but there are some important differences Mitosis Produces 2 genetically identical somatic cells Produces diploid cells Undergoes 1 cell division Mitosis (PMAT) Meiosis Produces 4 genetically different germ cells Produces haploid cells Undergoes 2 cell divisions Meiosis I, Meiosis II (PMAT1), (PMAT2) Concept Check: 1. Meiosis produces human cells with how many chromosomes? a. b. c. d. 44 23 46 15 Concept Check 2. Two similar chromosomes that you inherit from your parents ( one from your mother and one from you father) are called: a. homologous chromosomes b. sister chromatids c. sex chromosomes d. homozygous alleles Concept Check 3. Which of the following cell types is diploid? a. sex cell b. gamete c. sperm cell d. zygote Regulation of Cell Reproduction Cell cycle regulation is necessary for healthy growth. Internal and external factors regulate cell division The Cell Cycle Cells divide at different rates. The rate of cell division varies with the need for those types of cells Some cells are unlikely to divide. The Cell Cycle Cell size is limited Volume increases faster than surface area. Cell growth is coordinated with division The Cell Cycle Surface Area Surface area must allow for adequate exchange of materials Cells that must be large have unique shapes The Cell Cycle Regulation External factors include physical and chemical signals Example: growth factors are proteins that stimulate cell division. Most mammal cells form a single layer in a culture dish an stop dividing once they touch other cells. The Cell Cycle Regulation Internal factors regulate growth from inside the cell Two of the most important: Kinases Cyclins Internal factors are triggered by external factors, both of which will affect the cell cycle. The Cell Cycle Regulation Apoptosis is programmed cell death. Normal feature in healthy organisms Caused by a cell’s production of self-destructive enzymes Occurs in development of infants. webbed fingers The Cell Cycle Regulation Cell division is uncontrolled in cancer Cancer cells form disorganized clumps called tumors Cancer cells do not carry out necessary functions Cancer cells come from normal cells with damage to genes involved in cell cycle regulation. The Cell Cycle Regulation Benign tumors remain clustered and can be removed. Malignant tumors metastasize, or break away, and can form more tumors. The Cell Cycle Regulation Carcinogens are substances known to promote cancer Standard cancer treatments typically kill both cancerous and healthy cells.
