CELL GROWTH & DIVISION Mitosis & Meiosis Preview (Honors) Read: Chapter 10-1 Page 256: Define ALL vocabulary Page 257: #1-10 & 14 Page 282: Define Section 11-4 vocabulary 1
Preview (Academic) Read: Chapter 10-1 Page 256: Define ALL vocabulary Page 257: #12 Page 282: Define Section 11-4 vocabulary CELL GROWTH & DIVISION Mitosis & Meiosis 2
Discussion Why do we need cell growth? Why do we need cell division? Limitation to Cell Growth 1.) DNA Overload Amount of DNA in a cell controls all of the cellular processes. If you make the cell bigger, but do not increase the amount of DNA, the cell may not survive. 3
Limitation to Cell Growth 2.) Exchange of materials Cell membrane allows what comes in and out of the cell (i.e. water, oxygen, waste) Total Area of Cell Membrane How much the cell needs exchange depends on the volume of the cell Cell Size & Scale http://learn.genetics.utah.edu/content/cells/scale/ 4
Why Are Cells So Small? One of the most important factors affecting the size of the cell is the SIZE of the CELL MEMBRANE. Cells have to remain small to survive because: They have to take in enough nutrients and eliminate wastes (using the cell membrane). As a cell gets bigger, the volume increases faster than the surface area of the cell membrane. For a cell to survive it needs a LARGE SURFACE AREA to VOLUME RATIO. Why Are Cells So Small? Small cells have a larger surface area to volume ratio than larger cells. When a cell reaches its max size, the nucleus starts cell division, called MITOSIS or MEIOSIS. 5
Mitosis vs. Meiosis Mitosis & Meiosis Key Note: Only occurs in Eukaryotic Cells 6
MITOSIS Mitosis Mitosis: cell division that results in 2 daughter cells each having the same number and kind of chromosomes as the parent cell. Daughter: 2 chromosomes Parent: 2 chromosomes Daughter: 2 chromosomes 7
Mitosis General Information: Nickname: Normal Cell Division Occurs in somatic (body/germ) cells ONLY Produces somatic cells ONLY 8
Mitosis Background Information: Starts with somatic cell in DIPLOID (2n) state Each cell contains homologous chromosomes Chromosomes that control the same traits but not necessarily in the same way 1 set from MOM & 1 set from DAD Ends in DIPLOID (2n) state as somatic cells. Goes through ONE SET of divisions Start with 1 cell and end with 2 cells Why Mitosis? Accounts for 3 Essential Life Processes: 1.) Growth: Result of cells producing new cells Cells develop specialized shapes/functions in a process called differentiation. Rate of cell division controlled by GH (Growth Hormone), which is produced in the pituitary gland. Ex. Fertilized egg Baby/Infant 9
Why Mitosis? 2.) Repair Cell regenerates at the site of injury Ex. Skin (replaced every 28 days), Bone (after a fracture) Why Mitosis? 3.) Reproduction Asexual Offspring produced by only ONE parent Offspring produced are genetically identical MITOSIS Ex. Bacteria, fungi, certain plants & animals Sexual Offspring produced by TWO parents Offspring produced are a genetic combination of the two parents MEIOSIS Ex. Most animals (humans), plants 10
Why Mitosis? Some organisms can combine any of the three processes. Ex. Sea star can re-grow a lost arm (repair) and a lost arm can form a new sea star (reproduction). MEIOSIS 11
Meiosis Meiosis: two cell divisions that result in daughter cells having ½ the chromosomes (23) as the parent cell (46) Note: Meiosis I & Meiosis II 4 Daughter Cells Parent Cell 2 Daughter Cells Meiosis General Information: Only happens in GAMETES (sex cells) Males: sperm cells Females: egg cells Nickname: Reduction Division Produce GAMETES Number (#) of chromosomes is reduced in the process This is important so the # of chromosomes doesn t double with each generation. 12
Meiosis Background Information: Start: 1 germ cell in diploid (2n) state End: 4 gametes in haploid (n) state Are there sets of homologous chromosomes? NO Goes through 2 sets of divisions: Meiosis I Meiosis II 13
How Do Cells Divide? Important Terms/Concepts Chromosomes Made of DNA Carry genetic information Chromatin: Thin, fibrous form of DNA (looks like plate of spaghetti) Form of DNA when cells is resting (NOT dividing) Shortens, thickens to form chromosomes before cell division 14
Chromosomes To prepare for cell division, chromosomes duplicate (replicate) Each replicated chromosome has two sister chromatids that are identical and are joined by a centromere. After cell division, each cell receives a full set of chromosomes (one chromatid from each pair) Chromosomes come in pairs (like shoes) Humans have 46 chromosomes OR 23 pairs (one each from mom and dad) Chromosomes 15
Chromosomes Homologous Chromosomes: Paired chromosomes that control the same traits, but not necessarily the same way Ex. Both have eye color, but one codes for blue eyes and the other for brown eyes. Homologous Chromosomes Each locus may code for the same or different traits. Hair Color Hair Color Eye Color Eye Color Ear Lobes Lobed Not Lobed Ear Lobes 16
Sister Chromatid Hair Color Eye Color Ear Lobes Not Lobed Not Lobed Hair Color Eye Color Ear Lobes Exact copies of a chromosome from 1 parent Identical in every way Formed during early stages of Mitosis and Meiosis Separate during new cell formation Held together with a centromere Helpful Prefixes Haplo- = half or single Homo- = same Hetero- = different Locus = location Pro- = first Meta- = middle Ana- = back Telo- = last or away from 17
Karyotype Phases of Mitosis 18
Phases of Mitosis (IPMAT) IPMAT 1. Interphase 2. Early Prophase 3. Late Prophase 4. Metaphase 5. Anaphase 6. Telophase Interphase IPMAT Resting stage All other cellular processes are happening Cell is growing DNA (chromatin) and centrioles replicate 19
Early Prophase IPMAT Nuclear membrane begins to disappear Nucleolus disappears Chromatin shortens and thickens into chromosomes Centrioles migrate Late Prophase IPMAT Aster rays appear Surround the centrioles Spindle fibers appear 20
Metaphase IPMAT Chromosomes line up in the Middle, on cell equator (metaphase plate) Homologous chromosomes are present, but do not pair (match up) Spindle fibers are attached to each half of a chromosome pair Anaphase IPMAT Sister chromatids begin to migrate to the poles (centrioles), being pulled by the spindle fibers 21
Telophase IPMAT Chromosomes lengthen/thin to chromatin Aster rays & spindle fibers disappear Nuclear membrane reforms Nucleolus reforms Centrioles reform Cytokinesis IPMAT C Cell cytoplasm divides and partition forms to make 2 daughter cells Each has 2 complete sets of chromosomes, or diploid (2n) Plant cell: cell plate/cell wall created Animal cell: cell membrane pinches off 22
Interphase (again) Cell is at rest with 2 identical cells IPMAT C The Steps of Mitosis IPMAT C 23
Phases of Meiosis Phases of Meiosis IPMAT I&II Meiosis I: 1. Interphase 2. Prophase I 3. Metaphase I 4. Anaphase I 5. Telophase I Meiosis II: 1. Interphase II (very short) 2. Prophase II 3. Metaphase II 4. Anaphase II 5. Telophase II **Same stages as mitosis, EXCEPT they happen TWICE.** 24
Meiosis Prophase I IPMAT Same as Mitosis Prophase Differences: Homologous pairs attach to each other to form a Tetrad Crossing over occurs recombination of DNA from one sister chromatid to the other 25
Prophase I Crossing Over Metaphase I IPMAT Same as Mitosis Metaphase Difference: Tetrads line up at the cell equator. 26
Anaphase I IPMAT Same as Mitosis Anaphase Difference: Homologous chromosome pair separate and go BACK toward the poles, instead of the sister chromatids. This creates HAPLOID CELLS. Maternal and paternal chromosomes mix. Telophase & Cytokinesis I IPMAT C Same as Mitosis Telophase & Cytokinesis, nucleus is back to normal and cells divide into two. Difference: Two HAPLOID cells Each chromosome still has two sister chromatids, but NO homologous chromosomes are present. 27
Prophase II Chromosomes condense NO DUPLICATION!!! IPMAT Metaphase II IPMAT Chromosomes line up at the equator Spindle fibers attach to each sister chromatid 28
Anaphase II Sister chromatids pull apart and move BACK to the poles IPMAT Telophase & Cytokinesis II IPMAT C Nuclear membrane and nucleolus reappear Aster rays and spindle fibers disappear Cytokinesis produces 4 haploid cells 29
Telophase & Cytokinesis II IPMAT C Meiosis I 30
Meiosis II Mitosis vs. Meiosis Nickname Starting Cell Ending Cell Starting Cell Type Ending Cell Type Mitosis Normal cell division 2n (diploid) 2n (diploid) Somatic Somatic Meiosis Reduction cell division 2n (diploid) n (haploid) Germ Gametes # of Cell Divisions 1 2 # Start Cell # Cells Produced 1 cell 2 cells 1 cell 4 cells 31