CHAPTER 3 CELL DIVISION.pdf

SCIENCE CHP3 : CELL DIVISION LUSIA BAREK BINTI MOSES, Dr. PUSAT PERSEDIAAN SAINS DAN TEKNOLOGI 2024/2025  THE CONCEPT OF CELL DIVISION MITOSIS AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO...

SCIENCE CHP3 : CELL DIVISION LUSIA BAREK BINTI MOSES, Dr. PUSAT PERSEDIAAN SAINS DAN TEKNOLOGI 2024/2025  THE CONCEPT OF CELL DIVISION MITOSIS AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO: MEIOSIS THE CELL CYCLE  INTRODUCTION Process where new cells are reproduced from old ones, enabling all organisms to …  Cytokinesis: Cytoplasm divides to separate the cells into 2 daughter cells (=cytoplasmic division) The Towards the end of karyokinesis. concept of cell Karyokinesis: Cell divides and distributes its genetic division hereditary material (=nuclear division)  I. Mitosis: Why mitosis? Nucleus division to produce TWO daughter nuclei with IDENTICAL chromosome set Growth number (2n, diploid state) with Healing/repair of damaged tissue original/parent cell. Asexual reproduction (binary fission) Karyokinesis: Cell divides and distributes its genetic hereditary material 2 types (nuclear division) II. Meiosis: Why meiosis? Nucleus division to produce FOUR daughter nuclei with HALF chromosome set number (n, haploid state) with Reproduction original/parent cell.  THE CONCEPT OF CELL DIVISION MITOSIS AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO: MEIOSIS THE CELL CYCLE THE CELL CYCLE Sequence of stages cells passes through one cell division and the next. 1. Interphase 2. M phase (Mitosis/Meiosis) 3. Cytokinesis  G1 phase (First gap)-preparation phase RNA and proteins are synthesised (transcription and translation) Interphase Cell increases in size as organelles grow and increase Lasts at least 10 hours S phase (Synthesis phase) DNA is synthesised or duplicated Each chromosome now consists of two chromatids joined at centromere Lasts for at least 8 hours G2 phase (Second gap) Cell produces new proteins and continue to increase in size Microtubules are synthesised for spindle fibre development Centrosome is duplicated and asters are formed. Lasts for at least 5 hours.  QUICK CHECK! THE CONCEPT OF CELL DIVISION 1. Differentiate karyokinesis and cytokinesis. 1. Which step RNA is synthesized in interphase? THE CELL CYCLE  THE CONCEPT OF CELL DIVISION MITOSIS AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO: MEIOSIS THE CELL CYCLE  Process of cell division in which the chromosomes are replicated and divided to obtained two new cell which are identical (clon) to the original cell. (Somatic cells) Mitosis 2n 2n P.M.A.T  1. Prophase Structures/entity What happen at prophase? Chromatin Condenses into thick coils, forming chromosome chromosome Sister chromatid joined together at centromere Nucleolus Disappear Nuclear envelope Breaks down Centrosome and centriole Move to the opposite site of nucleus Spindle fibre Mitotic spindle begins to form and chromosome become attached to spindle fibres by their centromeres  2. Metaphase Structures/entity What happen at metaphase? Chromatin Not involved Chromosome Lined up at metaphase plate, attached to spindle fibres Nucleolus Not involved Nuclear envelope Not involved Centrosome and centriole Not involved Spindle fibre Not involved  3. Anaphase Structures/entity What happen at anaphase? Chromatin Not involved Chromosome Paired centromeres of each chromosome separate, each then is referred as a daughter chromosome. Nucleolus Not involved Nuclear envelope Not involved Centrosome and centriole Not involved Spindle fibre Shortening of spindle fibre pulls the sister chromatids apart towards opposite site of the poles  4. Telophase Structures/entity What happen at telophase? Chromatin Re-reform chromosome Uncoils and return to chromatin form Nucleolus Reappears Nuclear envelope Re-reforms around each set of chromosome Centrosome and centriole Not involved Spindle fibre Disappear  Cytokinesis Animal cell Plant cell A cleavage furrow forms and the furrow deepens inwards until it reaches the centre of the cell, dividing the cell into two Vesicles form at the equator of the dividing cell Vesicles enlarge and fuse to form a cell plate Cellulose is laid down between the new membranes, forming a new cell wall between the membranes. The effect of uncontrolled mitosis Example of Mitosis Application Sketch a parent muscle cell undergoing cell division in anaphase. Take 5  THE CONCEPT OF CELL DIVISION MITOSIS AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO: MEIOSIS THE CELL CYCLE  The process of nuclear division in a cell by which the chromosome number is reduced to half from the diploid number (2n) to the haploid number (n). (Gamete cells) Meiosis - meiosis I - meiosis II 2n n P.M.A.T x 2  Why we all different to each other? KEEP in mind. How does the cell mix up the DNA from each parent?  MEIOSIS I Structures/entity What happen at prophase I? Chromatin Condenses into thick coils, forming chromosome chromosome Pairing of homologous chromosomes (synapsis) forming bivalents (tetrads). 1ST GENETIC VARIATION Crossing over occurs at chiasmata to exchange genetic material between homologous chromosome. Nucleolus Disappear Nuclear envelope Breaks down Centrosome and Move to the opposite site of nucleus MEIOSIS centriole Five different substages Five different substages  MEIOSIS I Structures/entity What happen at metaphase I? chromosome Bivalents aligned 2nd GENETIC themselves at VARIATION metaphase plate Independent assortment: Random lining up of MEIOSIS chromosomes Helps to create gametes with different combinations of chromosomes from mom and dad  MEIOSIS I Structures/ What happen entity at anaphase I? Chromosome Homologous chromosomes separate and begin migrating towards opposite poles, pulled by spindle MEIOSIS fibres.  MEIOSIS I Structures/entity What happen at telophase I? chromosome De-condense. Each half of the cell has a complete haploid chromosome set One or both chromatids include regions of non- sister chromatid DNA. Nucleolus Reappears Nuclear envelope Re-reforms around each set of chromosome Centrosome and centriole Not involved  (almost identical to mitosis) MEIOSIS II -Separation of sister chromatids Separate at centromere NOT identical copy to parent cell MEIOSIS Why we all different to each other? How does the cell mix up the DNA from each parent? Genetic variation -crossing over during Prophase I -random lining during Metaphase I and Metaphase II  NORMAL KARYOTYPE OF HUMAN What happens when chromosomes don’t separate normally in Meiosis????? -EXTRA CHROMOSOME - TRISOMY 21 (NONDISJUNCTION) COMPARISON BETWEEN MITOSIS AND MEIOSIS  EXIT PASS: Test your knowledge about cell division!! Thank you for your attention