Cell Cycle Cell Reproduction When a cell divides

Cell Cycle

Cell Reproduction • When a cell divides in two cells • Cells need to grow larger because there is a limit to cell size • Needed to replace dead cells • Composed to MITOSIS and CYTOKINESIS

Chromosome Replication • Chromosomes are uncoiled and duplicated • CHROMATIDS are the two identical strands of a duplicated chromosome joined at the centromere

Cell Cycle Interphase • Rest/growth phase • Cell grows bigger • Chromosomes are uncoiled and duplicated

Cell Cycle Prophase • Preparing for mitosis • Chromosomes begin to coil And condense into visible threads • Centrioles move to the opposite ends of the cell • The spindle fibers form between the centriole pairs • Nuclear membrane breaks down and disappears

Cell Cycle Metaphase • Middle stage of mitosis • Paired chromatids begin to move towards the center of the cell between the two centrioles

Cell Cycle Anaphase • Leaving stage of mitosis • Each pair of chromatids splits at the centromere and becomes a single chromosome so there are TWICE as many chromosomes • Chromatids move to opposite ends of the cell

Cell Cycle Telophase • The last stage • Nuclear membranes form around the two new sets of chromosomes • Spindle disappears • Chromosomes begin to uncoil and gradually become less visible • Now two nuclei in the cell

Cell Cycle Cytokinesis • “Dividing materials • Division of organelles and the other substances in the cytoplasm into roughly equal halves • In animal cells, an indent forms in the cell membrane and deepens until the cell is pinched into half • In plant cells, a cell plate enlarges until it reaches the outer surface splitting the cell in half

Meiosis • For the production of gametes 1. Interphase 1. chromosomes duplicate

Meiosis 2. Prophase I - Chromosomes coil and become visible - Nuclear membrane disappears (crossing over may occur) - Spindle forms 3. Metaphase I - Chromosomes move to the middle and line up beside each other (crossing over may occur)

Meiosis 4. Anaphase I - Chromosomes move apart 5. Telophase I - Paired chomosomes uncoil - Nuclear membrane forms - Spindle disappears 6. Cytokinesis - TWO CELLS

Meiosis 7. Prophase II – Paired chromatids coil – Spindle forms – Nuclear membrane disappears 8. Metaphase II – Chromosomes line up in the middle of the cell 9. Anaphase II - each chromosome splits - move to the opposite ends of the cell

MEIOSIS 10. Telophase II - chromosomes uncoil - nuclear membrane form 11. Cytokinesis - Total of 4 cells from one cell

QUIZ 2