Cell cycleBiology 3 Kawashima

Philippine Science High SchoolSY 2009-2010

Roles of Cell Division

Reproduction

Growth and Development

Renewal and Repair

What happens in cell division?

Cell growth Duplication of genetic material Fission

90% of the cell cycle

Cell growth

DNA synthesis

Checkpoints for cell division

Interphase

Interphase

G1

SG2

Mitotic Phase

Prophase

Metaphase

Anaphase

Telophase

Genome

•All genetic information

Chromosome

•Condensed DNA packaging•Single DNA molecule

Chromatin

•Uncondensed state of DNA molecule

Chromatin condenses during prophase

• Nucleoli disappear• Duplicated

chromosomes appear as sister chromatids joined at the centromere

• Microtubules begin to extend from the centrosome

• Lengthening of microtubules propel centrosomes to move away from each other

Sister chromatids organize during prometaphase

• Nuclear envelope fragments

• Sister chromatids develop a kinetochore – a protein structure found at the centromere

• Microtubules interact with sister chromatids at their kinetochores

Sister chromatids align at the metaphase plate during metaphase

• Metaphase plate an imaginary plane equidistant between the poles

• Centrosomes now at opposite ends of the cell

• Each chromosome has numerous kinetochore microtubules attached

• Longest stage of mitosis

Sister chromatids separate during anaphase

• Liberated chromosomes move towards the poles through “walking” centromere region first

• Nonkinetochore microtubules lengthen elongating the cell

Chromosomes become less condensed during telophase

• Two daughter nuclei form

• Nuclear envelop reforms, arising from the endomembrane system

• Division of one nucleus into two genetically identical nuclei – mitosis – is now complete

Cytokenesis is the division of the cytoplasm

• Cytokenesis begins in telophase

• In animals, formation of cleavage furrow “pinches” the cell into two

• In plants, a cell plate forms to divide the cytoplasm into distinct cells

Read on Cell Cycle Checkpoints and Cancer