bio3lec1 cell cycle
TRANSCRIPT
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