CELL DIVISION & CANCER Day 1

Objectives Discuss the results, advantages and disadvantages of asexual and sexual reproduction. Explain how cell division is controlled.

Cell Division Vocabulary Somatic cell – All cells in your body except your gametes; a cell whose genes will not be passed on to future generations.  diploid (2n) – a cell with 2 chromosome sets; all body (somatic) cells  2n=46 for a human Germ cell - a 2n (diploid) cell that is destined to become a sex cell or gamete (egg or sperm); a cell whose genes can be passed on to future generations. haploid (n) – a cell with 1 chromosome set; all gametes (sperm, eggs) n=23 for a human (sperm: male and egg: Female)

Cell Division 2 kinds of cell division: 1. Mitosis: division of the somatic cell’s nucleus (2n creates 2n, asexual reproduction, identical copy) 2. Meiosis: creation of new sex cells (2n creates n, sexual reproduction, different from each other) Sperm cells Human egg cell Pancreatic cells

Cell Cycle A typical cell goes through a process of growth, development, and reproduction called the cell cycle. Any mutation affecting the cell cycle may cause cell to grow and divide without control (cancer) Click Image

Cell Cycle: Interphase The longest phase in the cell cycle is interphase. The 3 stages of interphase are called 1. G 1 (growth) 2. S (synthesis) 3. G 2 (growth)

Interphase: G 1 -phase Cells spend most of their time in G 1 the cell grows and performs its normal function. Prepares for S phase Control of cell division occurs in G 1 : a cell that isn’t destined to divide goes into G 0(resting phase, non-dividing phase). MUSCLE CELL NEURON G0G0

Interphase: S-phase The S phase (“Synthesis”) is the time when the DNA is replicated or copied. Sister chromatid is now attached at the centromere Parent strands Daughter strands

Chromosomes duplicate Interphase: S-phase Centromere Remember chromosome is not condensed, it is still chromatin

Interphase: G 2 -phase G 2 is the period between S and mitosis. DNA replication is checked and the cell is getting ready to divide.

G 2 : More growth and preparation for mitosis

Cell Division All living cells come from other living cells. During mitosis, the nucleus of the cell divides, forming two nuclei with identical genetic information.

Mitosis Mitosis produces two genetically identical cells called daughter cells which are 2n. Mitosis is referred to in the following stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Remember PMAT

Mitosis: Prophase In prophase, the cell begins the process of division. The chromosomes condense. Chromatin coils up to form X shape chromosome. duplicated chromosome

Prophase (continued) Nuclear envelope disappears. Nucleolus Disappears Centrosomes (plants and animals) and Centrioles (animals only) migrate to opposite poles of the cell. Asters and spindle fibers form (proteins… Microtubules).

Mitosis: Metaphase All 46 chromosomes line up at the equator of the cell (metaphase plate, equatorial plane) the centrioles are at opposite poles the spindle fibers attached to the kinetochore which is attached to the centromere. centromere Centriole Metaphase plate Spindle fibers Apparatus

Metaphase in picture

Mitosis: Anaphase In anaphase, the centromere divides because spindle fibers pull the sister chromatids in opposite direction. At this point, each single chromosome goes from having 2 sister chromatids to being 2 separate chromosomes The spindle fibers contract and the chromosomes are pulled to opposite poles. Spindle fibers Centromere breaks

Mitosis: Telophase Chromosomes arrive at opposite poles of the cell. The nuclear envelope re- forms around the two sets of chromosomes. Spindle apparatus disappears Chromosomes uncoil and is now chromatin once again Division of the Nucleus is complete Opposite of prophase

Cytokinesis in animal cells Cytokinesis is the division of the cytoplasm. Cytokinesis starts during telephase In animal cells, a Cleavage Furrow forms and separates Daughter Cells Cleavage furrow in a dividing frog cell.

Cytokinesis in Plant Cells In plant cells, a Cell Plate forms and separates Daughter Cells. Cell Plate forming

ANIMAL VS. PLANT MITOSIS ANIMAL CELL Centriole and aster present Daughter cells separated by cleavage furrow PLANT CELL No visible centriole or aster Daughter cells separated by cell plate

G0G0

MITOSIS ANIMATION

Proteins Control the Cell Cycle Proteins control the cell cycle A mutation in DNA that changes the shape of a protein may make the protein malfunction The cell cycle is uncontrolled and may allow mitosis to go unchecked and occur very rapidly. This can cause Cancer When cancerous cell get into the blood stream they can travel all over the body creating more tumors (metastasized)

What do living things use Mitosis for? Maintains Chromosome number in specie’s somatic cells (2n – 2n) ( n-n ) Growth of a living thing Zygote to embryo to fetus to baby to adult Repair Heal wounds Replace worn out cells  Skin, blood, etc Asexual Reproduction All offspring identical to parent ( 2n) Limits variation

MITOSIS RAFT In a CREATIVE MANNER, explain ALL the steps of the Cell Cycle. You may use poetry, drawings, a diary entry, a short story, comic strip, songs, rap, a news article, a scientific journal entry, etc.