Chapter 10 Cell Division Mitosis Mitosis Division of
- Slides: 42
Chapter 10: Cell Division & Mitosis
Mitosis • Division of cell nucleus • Common to ALL living things-- but details of mitosis vary from organism to organism • The sequence of phases is fixed in all organisms, but time spent in each phase varies
Biologists Compare Cell Division 1) In different organisms by comparing their cell cycles 2) Between different kinds of tissues within the animal/plant 3) Between normal tissue and tissue repair after injury 4) Between the young child and elderly person
Biologists Compare Cell Division cont. 5) Between embryological (unspecialized cells) and in fetal cells that develop into tissues (specialized cells) 6) Between prokaryotic and eukaryotic cells - Prokaryotic & some protists binary fission 7) Between cancer and normal cells
Cell Division in Eukaryotes 1) Unicellular organisms– cell division new individuals (reproduction) 2) Multicellular organisms-- cell growth/ repair/ maintenance/ reproduction a. Plants- formation of roots, stems, leaves b. Animals- formation of specialized cells (nerve, bone, muscle)– blood and skin cells are replaced as needed throughout life (106 mitotic cell division/sec)
Cell Division in Eukaryotes cont. 3) In all cell divisions there is chromosome replication/ duplication - Body/ somatic cells= 46 chromosomes (23 pairs/ 1 set from each parent) - Gametes/ sex cells= 23 chromosomes (1 set from parent)
Controls of Cell Division ( Cell Cycle) 1) Rate varies between species and between tissues within same organism-anywhere from min/hr/day/never a. Go Phase • Cells never leave G 1 phase • In this way, specialized cells remain very active-never having to stop working to divide; all energy is used to carry out important specialized functions Ex: Nerve and muscle cells (can enlarge through use of anabolic steroids), Heart cells (can enlarge in athletes), Leaf cells (palisade, xylem, phloem), Red blood cells (in circulation) complete cycle only in growth tissues
Controls of Cell Division ( Cell Cycle) cont. b. Some cells divide very rapidly Ex: Bacteria E. coli (prokaryote- every 30 min) Skin and blood (106 div/sec) Digestive tract (6 hrs) Respiratory tract (8 hrs)
Controls of Cell Division ( Cell Cycle) cont. 2) Could be caused by some “trigger protein” -- some molecular on/off switch like a hormone of an enzyme - Turned on rapidly in times of cell stress or gradually increases during G 1 phase to a level when S phase can begin
Controls of Cell Division ( Cell Cycle) cont. 3) Or by special regions called TELOMERES-found at the ends of chromosomes - These telomeres shorten with every subsequent division until division stops a. Changes seen in normal/ cancer cells b. Changes seen in early aging (Progeria)/ normal
Overview of Cell Cycle
Phases of Cell Cycle • Sequence is fixed from start to finish (for entire life cycle) a. Interphase (non-dividing cells) has 3 distinct phases: G 1, S, G 2 b. Mitosis (dividing cells) has 4 phases in nucleus: P, M, A, T c. Cytokinesis: C
Phases of Cell Cycle cont.
INTERPHASE (3 phases) 1. G 1 phase (Growth 1 - just after cell is formed) • • • Very active metabolically-- biochemical pathways: photosynthesis, cell respiration, biosynthesis ↑ in molecules-- enzymes, hormones, proteins, m. RNA ↑ in number of cellular organelles ↑ in size-- usually doubles in size Length varies from hours to several days
INTERPHASE (3 phases) 2) S phase (Synthesis- must occur prior to mitosis) • • • DNA double exactly (replication) all genes copies DNA polymerase (enzyme) is very active-- nucleotide assembly Histone proteins (for DNA support) increase Nucleosomes formed (DNA packing occurs) Usually 3 -6 hours 2 chromatids attached at centromere-- end result
INTERPHASE (3 phases) 3) G 2 phase (Growth 2 - getting ready for division) • Twice as much DNA as G 1 • Protein synthesis (microtubules/ microfilaments) form spindles • Centrioles replicate (in animal cells only) • 2 -5 hours, relatively constant among cells
MITOSIS (P, M, A, T) • Phases covered later
CYTOKINESIS • Division of the cytoplasm • Occurs during telophase of mitosis
2 Major Phases of Mitotic Cell Division 1) MITOSIS • • Process of cell division in eukaryotic cells in which the nucleus is divided into 2 nuclei, each with the same number and kinds of chromosomes This phase is divided into the: a. Growth period-- Interphase b. And 4 stages-- Prophase, Metaphase, Anaphase, Telophase (P, M, A, T) • The stages conserve chromosome number by equally distributing replicated chromosomes to each of the daughter cells
2 Major Phases of Mitotic Cell Division cont. 2) CYTOKINESIS • The division of the cytoplasm to form 2 separate daughter cells immediately after mitosis
MITOSIS (replication and division of the nucleus) 1) INTERPHASE a. G 1 phase o o o Growth phase of a cell Cell grows rapidly and carries out its routine functions For most organisms, this phase occupies the major portion of the cell’s life between cell divisions b. S phase o o Time during which DNA is being replicated At the end of this phase, an individual chromosome consists of 2 chromatids attached by a centromere
MITOSIS – INTERPHASE cont. c. G 2 phase o o o Time during which preparations are made for nuclear division Mitochondria and other organelles replicate Microtubules reassembled-- will be used to form the spindle apparatus that moves the chromosomes d. M phase o o Phase where mitosis occurs Mitosis is the replication and division of the nucleus to form 2 identical nuclei, each with the same number and kinds of chromosomes
Cell Cycle
Interphase
MITOSIS 2) PROPHASE: 2 Major Phases a. Early Prophase o Replicated chromatids are present o Replicated centrioles (only in animal cells) migrate to opposite poles of the cell o Spindle fibers become visible b. Late Prophase o Nucleolus and nuclear envelope disintegrate o Chromatids condense to form dense coils
Prophase
MITOSIS cont. 3) METAPHASE o Chromatids are at the same midline (called the equatorial plate in plants) o Spindle fibers are very dense o In animal cells, the aster is visible around the centrioles
Metaphase
MITOSIS cont. 4) ANAPHASE o Centromeres separate and the chromatids now become individual chromosomes o Chromosomes migrate to opposite poles of the cell
Anaphase
MITOSIS cont. 5) TELOPHASE o Phase of mitotic cell division in which the cytoplasm divides and 2 identical cells form o Cytokinesis occurs during this phase
2 Major Differences Between Animal and Plant Cell Division
Animal vs Plant
MITOTIC CELL DIVISION IN PLANT CELLS
MITOTIC CELL DIVISION IN PLANT CELLS cont.
MITOSIS
PRACTICE! Name that Stage!
PRACTICE! Name that Stage!
PRACTICE! Name that Stage!
PRACTICE! Name that Stage!
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