Life Cycle of a Cell

Cell Size Why not just one large cell? Difficult to get nutrients in and waste out

Phases of The Cell Cycle G1,S, and G2 are known together as Interphase.

Sex cells are called gametes Regular Cells Somatic cell cycle  Interphase – cell grows, copies its DNA and prepares for Mitosis by copying organelles M phase- Cell division (Mitosis and cytokinesis) Sex cells are called gametes

Interphase Chromosomes Condense Chromosomes are inherited genetic information Chromosomes are made up of DNA Can only be seen when cells are dividing

Interphase Chromosomes replicate-or copy is made The two copies are -attached together at a point called a centromere. -are called sister chromatid.

Organelles must be replicated (copied) Interphase Organelles must be replicated (copied) 9

M Phase Two parts: Nuclear division Cytoplasmic Division Mitosis Saturday, November 24, 2018 M Phase Two parts: Nuclear division Mitosis Cytoplasmic Division Cytokinesis 10

Mitosis Nuclear Division. Nucleus divides into two new nuclei Mitosis keeps the number of chromosomes constant from one cell generation to the next. In eukaryotes, it is the main process by which growth and tissue repair is accomplished. Mitosis is also the main process by which single-celled and many multi-celled eukaryotes reproduce asexually.

4 Steps of Mitosis (PMAT)  Prophase: Chromosomes condense and attach to the spindle fibers at their centromere. Nuclear Membrane breaks down.

Steps of Mitosis (PMAT)  Prophase: Centrioles move to opposite sides of the cell and organize the spindle fibers

Metaphase: Chromosomes attach to spindle fibers and line up in the middle of the cell

Anaphase: Chromosomes separate-Move to opposite sides of the cell

Telophase Nuclear Envelope reforms There are now TWO nuclei in one cell! Nuclear Envelope reforms …And they contain the SAME genetic information*SAME NUMBER OF CHROMOSOMES

Cytokinesis Cytoplasmic division Each cell gets half of the organelles. After mitosis: cell pinches in half to form two new cells.

Cytokinesis Animal cells pinch. Cytokinesis in plant cells is different from that in animal cells.

In plant cells a cell plate forms from the inside out.

Results of Mitosis and Cytokinesis Two new cells. The new cells- called daughter cells- have the same number of chromosomes as the mother cell. This occurs in all somatic cells in your body. You have 46 chromosomes in all of your somatic cells-23 pair!

Mitosis in Onion

Cells during Mitosis

Meiosis

Reproduction of Sex Cells Sex cells- Sperm and egg Process is called Meiosis Similar to Mitosis

Meiosis Cell divides twice First division is like mitosis and then the cell divides again to create 4 haploid cells.

MEIOSIS=CHROMOSOME REDUCTION DIVISION

Meiosis Meiosis is also know as chromosome reduction division. Start with 46 and ends up with 23. Why? Fertilization creates the diploid condition again Haploid Diploid

Sperm formation- 4 haploid sperm cells are formed. Egg formation-most of the cytoplasm is used in one cell and the other three disintegrate. One haploid egg cell is formed.

Meiosis Video Clip

Crossing Over Sometime during meiosis the chromosomes can exchange information This is called Crossing Over Major source of genetic diversity in the species

Prokaryotic Cells Binary fission Occurs in Prokaryotic Cells DNA is copied and then the cell splits in half.

Regulation of the Cell Cycle How do cells know when to divide? When to stop dividing? Cyclins-proteins that regulate the cell cycle When cells grow and then come into contact with each other they should stop growing.

Cancer Unregulated cell growth. Can form masses of cells called tumors.