cell growth and division -...
TRANSCRIPT
CELL GROWTH AND DIVISION
STANDARD 8
LIMITS TO CELL GROWTH• 2 REASONS CELLS DIVIDE RATHER THAN
GROW:
1. LARGER A CELL BECOMES THE MORE DEMANDS THE CELL PLACES ON ITS DNA
2. CELLS HAVE MORE TROUBLE MOVING ENOUGH NUTRIENTS AND WASTES ACROSS THE CELL MEMBRANE
IN PROKARYOTES, DNA REPLICATES AND THE CELL DIVIDES BY SEPARATING THE CONTENTS INTO 2 PARTS
IN EUKARYOTES THE CELL DIVISION OCCURS IN 2 MAIN STAGES:
1. DIVISION OF THE NUCLEUS: MITOSIS
2. DIVISION OF THE CYTOPLASM:
CYTOKINESIS
CHROMOSOMES:
THE GENETIC INFORMATION THAT IS PASSED DOWN TO DAUGHTER CELLS IS CARRIED BY CHROMOSOMES
CHROMOSOMES ARE MADE UP OF DNA
DNA CONTAINS THE CELL’S CODED GENETIC INFORMATION AND PROTEINS
CELLS OF EVERY ORGANISM HAVE A SPECIFIC NUMBER OF CHROMOSOMES:
EX: HUMAN CELLS HAVE 46 CHROMOSOMES
FRUIT FLIES HAVE 8 CHROMOSOMES
CHROMOSOMES ARE SPREAD THROUGHOUT THE
NUCLEUS EXCEPT FOR DURING DIVISION WHEN THEY
CONDENSE
ONCE CHROMOSOMES ARE CONDENSED THEY CAN
REPLICATE
THE 2 COPIES OF THE CHROMOSOMES ARE
IDENTICAL
THE COPIES ARE CALLED SISTER CHROMATIDS
THE PAIR OF CHROMATIDS ATTACH AT THE CENTROMERE
CELL CYCLE: SERIES OF EVENTS THAT CELLS GO THROUGH AS THEY GROW AND DIVIDE.
DURING THE CELL CYCLE:
A CELL GROWS CELLS PREPARES FOR DIVISION
DIVIDES TO FORM DAUGHTER CELLSCYCLE
BEGINS AGAIN
CELL CYCLE CONSISTS OF 4 PHASES:
1. G1 PHASE:
MOST OF CELL GROWTH HAPPENS
2. S PHASE
REPLICATION OF DNA SO EACH CELL RECEIVES A COPY
3. G2 PHASE
GROWTH AND PREPARATION FOR MITOSIS
4. M PHASE
MITOSIS AND CYTOKINESIS
STEPS 1,2,3 ARE CONSIDERED PART OF INTERPHASE
INTERPHASE: PERIOD IN CELL CYCLE BETWEEN CELL DIVISION
MITOSIS:
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
PROPHASE
1ST AND LONGEST PHASE OF MITOSIS
CHROMOSOMES BECOME VISIBLE
CENTRIOLES SEPARATE AND GO TO OPPOSITE SIDES OF
THE NUCLEUS
THE NUCLEOLUS
DISAPPEARS AND THE
NUCLEAR ENVELOPE
BREAKS DOWN
METAPHASE
2ND PHASE OF MITOSIS
OFTEN ONLY LASTS A FEW MINUTES
CHROMOSOMES LINE UP ACROSS THE CENTER OF THE
CELL
SPINDLE FIBERS ATTACH TO THE CENTROMERES
ANAPHASE
3RD PHASE OF MITOSIS
THE CENTROMERES (THAT JOIN THE SISTER CHROMATIDS)
SPLIT
THE CHROMATIDS
SPLIT TO BECOME
INDIVIDUAL
CHROMOSOMES
TELOPHASE
FINAL PHASE OF MITOSIS
CHROMOSOMES UNWIND FROM BEING CONDENSED
NUCLEAR ENVELOPE REFORMS
SPINDLE BEGINS TO BREAK APART
NUCLEOLUS BECOME
VISIBLE IN EACH
DAUGHTER CELL
CYTOKINESIS
IN ANIMAL CELLS THE CELL MEMBRANE COMES TOGETHER
AND PINCHES APART INTO EQUAL PARTS
IN PLANT CELLS A CELL PLATE FORMS MIDWAY BETWEEN
THE DIVIDED NUCLEI
CELL WALL DEVELOPS INTO A
SEPARATING MEMBRANE CREATING
A CELL WALL
LOOKING AT CELLS
• ACTUAL CELLS
• MORE MITOSIS