CHAPTER 8 THE CELL CYCLE P.213-229

CELL DIVISION PROKARYOTES ASEXUAL REPRODUCTION/BINARY FISSION (VOLUME DOUBLES AND THE CELL SPLITS)SUCH AS BACTERIA EUKARYOTES UNICELLULARASEXUAL REPRODUCTION/BINARY FISSION TO GET 2 NEW ORGANISMS SUCH AS PROTISTS MULTICELLULARASEXUAL /BINARY FISSION FOR NEW TISSUES (GROWTH, REPAIR, MAINTENANCE)

THE CELL CYCLE REGULATED BY CHEMICALS CALLED CYCLINS

INTERPHASE (THE PERIOD BETWEEN DIVISIONS ) G1GROWTH CELL GROWTH AND SYNTHESIS (RNA, PROTEINS, MACROMOLECULES) G0 A POINT DURING G1 WHERE CELLS STOP DIVIDING AS THEY HAVE REACHED A MATURE STATE (SUCH AS BRAIN AND NERVE CELLS) SDNA SYNTHESIS DNA OF CHROMOSOMES REPLICATES FORMING A NEW IDENTICAL SET G2GROWTH CELL GROWTH AND SYNTHESIS (ORGANELLES)

MITOSIS (M) 4 PHASES OF NUCLEAR DIVISION, WITH SORTING AND DISTRIBUTION OF CHROMOSOMES MADE UP OF 2 CHROMATIDS AND A CENTROMERE

4 STAGES OF MITOSIS 1.PROPHASE 2.METAPHASE 3.ANAPHASE 4.TELOPHASE BREAKDOWN OF NUCLEAR MEMBRANE, THE SPINDLE FORMS FROM MICROTUBULES (COMPOSED OF SPINDLE FIBERS) 2.METAPHASE CHROMOSOMES BECOME ARRANGED AT THE EQUATOR (MIDDLE) OF THE CELL 3.ANAPHASE CHROMATIDS ARE SEPARATED AND PULLED APART BY THE SPINDLE FIBERS TO OPPOSITE ENDS OF THE CELL (NOW THEY ARE INDIVIDUAL CHROMOSOMES) 4.TELOPHASE TWO NEW NUCLEI WITH THE SAME NUMBER OF CHROMOSOMES FORM

AFTER TELOPHASECYTOKINESIS OCCURS WHERE 2 NEW DAUGHTER CELLS ARE FORMED IN ANIMAL CELLSFORMS FROM A CLEAVAGE FURROW IN PLANT CELLSFORMS FROM VESICLES ALONG THE CELL PLATE

S PHASE (DNA REPLICATION) HOW THE PROCESS WORKS 4 MAJOR STEPS 1. ENZYMES AND PROTEINS CALLED HISTONES BIND AT ORIGINS OF REPLICATION (ALSO KNOWN AS REPLICATION FORKS OR BUBBLES ) 2. ENZYMES (CALLED HELICASES) USE ENERGY FROM ATP TO UNWIND THE DNA DOUBLE HELIX (AT HYDROGEN BONDS BETWEEN THE NITROGEN BASES). 3. ENZYME DNA POLYMERASE CATALYZES FORMATION OF NEW STRANDS BY ADDING NUCLEOTIDES (SUGAR, PHOSPHATE, NITROGEN BASE). 4. NEW BASES ADDED IN OPPOSITE DIRECTIONS AS DNA POLYMERASE CAN ONLY WORK IN ONE DIRECTION.

DNA REPAIR IN THE S PHASE 4 MAJOR STEPS IN THE PROCESS 1. ENZYME DNA POLYMERASE PROOFREADS BASE-PAIR MATCHING AND REPLACES WRONG NUCLEOTIDE WITH CORRECT ONE. 2. ENZYME (CALLED NUCLEASE) RECOGNIZES MISMATCH AND BINDS TO DNA TO BREAK APART DNA PIECE THAT IS DAMAGED AND REMOVES IT. 3. DNA POLYMERASE FILLS IN CORRECT SEQUENCE. 4. ANOTHER ENZYME, DNA LIGASE, RESEALS DNA WITH SUGAR- PHOSPHATE BACKBONE.