MCB 181 1st Edition Lecture 19Outline of Previous Lecture I. PhotophosphorylationII. Light Independent Reactions Outline of Current Lecture I. IntroductionII. Overview of MitosisIII. Process of MitosisCurrent LectureI. Introductiona. Why do cells divide?i. To repair damaged tissue for multicellular organismsii. Asexual reproductioniii. For the growth and development of organismsII. Mitosis Overviewa. Mitosis is the nuclear division of a eukaryotic cell, producing two daughter nuclei that are genetically identical to the parentb. Chromosomes are long double helixes of DNA that carry the cell’s genetic informationc. Two keys in cell cyclei. Replication of DNAii. Separation of the copied chromosomes into two daughter cellsd. Mitosis is a continuous process with several sub-phasesi. Prophaseii. Prometaphaseiii. Metaphaseiv. Anaphasev. Telophasee. Centrosomes – structures in animals and fungal cells, consisting of two-centrioles together near the nucleusi. Serve as a microtubule organization center for the cell’s cytoskeleton and for mitotic spindle during cell divisionf. Centrioles – one of two pairs of small cylindrical structures found together near the nucleus of a eukaryotic celli. Collectively called the centrosome, they serve a as a microtubule hub for the cell cytoskeletong. Mitotic spindle – structure that produces mechanical forces that pull chromosomes into the daughter cells during mitosisi. Consists of an array of microtubules that moves chromosomes to opposite sides of the cell during division (in mitosis and meiosis)III. Process of Mitosisa. Prophasei. Chromosomes that have already replicated condenseii. The mitotic spindle forms from a microtubule-organizing center and attach tothe chromosomesb. Prometaphasei. The nucleolus disappearsii. The nuclear envelope breaks downiii. Spindle fibers attach to each sister chromatid’s centromere (kinetochores)iv. Microtubules now start moving chromosomes toward the middle of the cellc. Metaphasei. Chromosomes line up along an imaginary line called the metaphase plated. Anaphasei. Centromeres split and sister chromatids are pulled towards opposite poles of the cellse. Telophasei. A new nuclear envelope begins to form around each set of chromosomesii. When two independent nuclei have formed, mitosis is completef. Cytokinesisi. Cytokinesis, the division of the cytoplasm to form two daughter cells, typically occurs immediately after mitosisIV. Clicker QuestionsHow do cells at the completion of mitosis (but before cytokinesis) compare with cells that have replicated their DNA and are just about to begin mitosis? They have the same amount of DNA and the same number of
View Full Document
Unlocking...