The Eukaryotic Cell Cycle Mitosis PDF

The Eukaryotic Cell Cycle Mitosis Chapter Outline: The Eukaryotic Cell Cycle Mitotic Cell Division BIOLOGY PRINCIPLE Cells are the simplest units of life The continuity of life is based on the flow of genetic material between cells. Why Do Cells Divide? Requ...

The Eukaryotic Cell Cycle Mitosis Chapter Outline: The Eukaryotic Cell Cycle Mitotic Cell Division BIOLOGY PRINCIPLE Cells are the simplest units of life The continuity of life is based on the flow of genetic material between cells. Why Do Cells Divide? Required for reproduction Required for growth and development Cell replacement and tissue renewal Loading… Types of Cell Division in Humans Asexual (genetic clones) Mitosis conserves chromosome number Sexual (genetic variation) Meiosis only in gamete (sex cells) production Reduces chromosome number  Eukaryotes have sets of chromosomes Human somatic cells have 23 pairs of chromosomes (46 total chromosomes) Autosomes – 22 pairs in humans Sex chromosomes – 1 pair in humans – XX or XY Diploid or 2n Loading… Human gametes have only1 member of each pair of chromosomes (23 total chromosomes) Haploid or n  Members of a pair of chromosomes are called homologs (homologous chromosomes) Homologs are nearly identical in size and genetic composition ex: Both carry gene for eye color but one may have brown and the other blue Sex chromosomes Not true homologs X and Y very different from each other in size and genetic composition Two Types of Nuclear Division in Eukaryotes: - Mitosis and Meiosis  Genome usually in the form of chromatin Compact chromosomes only form to prepare for cell division  The DNA sequence of chromosome is organized into multiple genes The centromere is an area where the chromosome narrows genes centromere Karyotype reveals number, size, and form of chromosomes in an actively dividing cell Karyotype of a normal human male Each chromosome has a homolog Cell cycle (life cycle of a cell) G1 – first gap S – synthesis of DNA Interphase Loading… G2 – second gap M – mitosis and cytokinesis G0 –cells postponing division or never dividing again G1 phase Cell growth and development Signaling molecules promote progression through the cell cycle If the cell passes the G1 checkpoint, it is committed to enter S phase and replicate DNA S phase Each chromosomes replicated Replicated chromosomes Two identical copies called sister chromatids Stay joined to each other at the centromere Human cell in G1 has 46 chromosomes Same cell in G2 has 46 replicated chromosomes (92 sister chromatids) sister chromatids centromere  G2 phase Cell synthesizes proteins and structures needed during mitosis and cytokinesis Mitosis Nuclear division, separation of sister chromatids Cytokinesis – follows mitosis to divide the cell into two daughter cells  Control of Cell Division External factors – should the cell divide? Environmental conditions Signaling molecules Internal factors – Is the cell ready to complete division? Cell cycle control molecules Checkpoints  Internal checkpoints Three checkpoints : G1/S checkpoint (restriction point) G2/M checkpoint Metaphase (spindle ) check  Checkpoint proteins act as sensors to determine if the cell is in the proper condition to divide G1/S checkpoint (restriction point) is the critical point If cell can’t pass this checkpoint it will exit cycle G0 phase Loss of control at checkpoints can lead to cancer  Checkpoint proteins Cyclins and cyclin-dependent kinases (cdks) responsible for advancing a cell through the checkpoints Amount of cyclins varies through cycle Cdks levels are constant Must bind to a cyclin protein to be active  Mitotic Cell Division Diploid somatic cell divides to produce two new genetically identical diploid cells (daughter cells) Involves mitosis plus cytokinesis asexual reproduction development and growth in multicellular organism  Interphase – prep for mitosis occurs Mitosis Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis – division into two daughter cells Mitotic spindle Ensures that each daughter cell will obtain the correct number and types of chromosomes Mitotic spindle apparatus (or mitotic spindle) is responsible for organizing and sorting the chromosomes during mitosis Centrosomes Microtubule organizing center  Spindle formed from microtubules Composed of tubulin proteins Three types of spindle microtubules Astral microtubules Polar (non-kinetochore) microtubules Kinetochore microtubules Mitotic spindle Sisterchromatid separate and move along the kinetochore microtubules toward opposite ends of the cell Microtubules shorten by de-polymerizing at kinetochore ends Motor proteins “walk” chromosomes to opposite poles Loading…  Cytokinesis Division of cytoplasm to create two new cells Animals – cleavage furrow constricts like a drawstring to separate the cells Plants – cell plate forms a cell wall between the two daughter cells