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