Starter1. What is the purpose of cell division?2. What are the 3 major steps and what

happens in each of the cell cycle?3. Why must DNA replication happen

before mitosis and cytokinesis?4. What are the phases of mitosis?5. With a pencil, label your drawings with

the stages of the cell cycle, the phases of mitosis and cytokinesis.

Where we have been. Cells

Organelles Nucleus

DNA Replication

Chromosomes

Curious? Asexual

reproducers Archea Bacteria Protists Starfish

Sexual reproducers (pregnancy length) Birds Humans (9 months) Insects Rabbit (33 Days) Alpine Salamander

(38 months) Elephant (22

months)

Starter Using 9.1 complete the reproduction

venn diagram on the front table

Asexual Vs. Sexual Reproduction Reproduction – 2 types

Asexual One Parent Offspring genetically identical to the ONE parent Quick Many offspring

Sexual Two Parents Offspring share genetic information from BOTH parents Creates variation (offspring genetically different) Slower Few offspring

Chromosomes Chromosomes

DNA condensed, wrapped around proteins, called histones Nucleus Only visible during cell division Each organism has its own number

Corn – 20, fruit fly 8, horsetail – 216, Chimp – 48, Dog – 78, humans? Somatic cells? Sex Cells?

Haploid-half set of chromosomes 23 in our nucleus

Diploid – Full Set of chromosomes 46 in our nucleus

Chromosomes Sister Chromatids

The 2 halves of a replicated chromosome Centromere

The place where sister chromatids are connected

CELL DIVISION

Cell Division Why?

Replace lost cells Repair Growth and development Reproduction

Cell Cycle “ALL CELLS COME FROM CELLS” The “life cycle” of a cell from the

beginning of one division to the beginning of the next division.

Cell division 1 cell becomes 2

The 2 new cells are called Daughter Cells

The Cell Cycle Interphase

G1 – primary growth S – DNA replication G2 – Cell carries out

everyday functions, prepares for division

Mitosis M – Cell divides

Cytokinesis Cytoplasm divides

MITOSISThe Break Down

The Phases Prophase Metaphase Anaphase Telophase Cytokinesis

Prophase

Nucleus disappears Chromatin condenses forming

chromosomes (visible) Centrioles move to opposite sides of the

nucleus Spindle fibers form between them – some

of which attach to centromeres on each side of the chromosome

Metaphase Chromosomes line up in the middle of

the cell

Anaphase Sister chromatids split at centromeres to

make separate chromosomes Chromosomes move to opposite ends of

the cell

Telophase Chromosomes begin to uncoil back into

chromatin Nuclear membranes develop around the

bundles of chromatin at opposite ends of the cell

Spindle fibers disappear Nucleolus reappear in each new,

daughter cell

Cytokinesis When the cytoplasm divides, cell division

is complete.

Not always the same! Animals

Cell membrane pinches, forming 2 identical daughter cells

Complete cells that are identical

Plants Cell Plate forms

halfway between the 2 nuclei

Materials for new cell walls and membranes gather and fuse in the middle between the 2 nuclei. Material gradually divides to create 2 cells.