Cell Reproduction Unit

Chromosome Structure - chromosome = a long continuous thread of DNA that consists of numerous genes with regulatory information coiled around proteins in compact structures

Chromosome Structure - DNA wraps around proteins (called histones) to become compact

Chromosome Formation

Chromosome Structure (cont) Chromatid Centromere

Cell Cycle = the regular pattern of growth, DNA duplication, and cell division that occurs in cells

- results in two cells (daughter cells) identical to one another Cell Cycle - results in two cells (daughter cells) identical to one another - made up of 5 Phases

3) G2 Phase = cell prepares for cell division Cell Cycle (cont) 1) G1 Phase = cell growth 2) S Phase = DNA is copied 3) G2 Phase = cell prepares for cell division Together Phases 1-3 are called Interphase

4) M Phase (Mitosis) - division of the nucleus Cell Cycle (cont) 4) M Phase (Mitosis) - division of the nucleus 5) C Phase (Cytokinesis) - division of the cytoplasm

Sequence of the Cell Cycle G1 S G2 M C Cell Cycle (cont) Sequence of the Cell Cycle G1 S G2 M C

Cell Cycle (cont)

Cell Cycle (cont)

= division of the nucleus and its contents Mitosis = division of the nucleus and its contents - discovered by Walther Flemming in 1882

Phases of Mitosis

1) Prophase - DNA coils to become chromosomes - nuclear membrane disappears - microtubules called spindle fibers grow from centrioles to center of cell

1) Prophase (cont) Spindle Fibers: 2 Types 1) Kinetochore Fibers – attach to chromosomes (at centromere) 2) Polar Fibers – spread throughout cell

Prophase Centrioles Nucleus with Chromosomes Spindle Fibers

Late Prophase Kinetochore Fibers Polar Fibers

2) Metaphase - chromosomes line up in center

Metaphase

3) Anaphase - chromosomes pull apart and move to opposite sides of cell

Anaphase

4) Telophase - chromosomes uncoil - nuclear membrane reforms

Telophase Chromosomes Uncoil New Nuclear Membrane Forms

Phases of Mitosis

How do you remember the order of the phases of Mitosis? Just remember this phrase……….

PMAT PEE MATT P = Prophae M = Metaphase A = Anaphase T = Telophase

Cytokinesis - cell membrane forms a cleavage furrow and cytoplasm divides - in plants, a cell plate forms between each cell

Cytokinesis Cleavage Furrow

Cell Plate

Regulation of Cell Division - controlled by external and internal factors - External Factors 1) cell to cell contact 2) growth factors

Cell to Cell Contact

Regulation of Cell Division (cont) Growth Factors – Examples - Platelets

Regulation of Cell Division (cont) Growth Factors – Examples - Erythropoietin (stimulates red blood cell production)

Regulation of Cell Division (cont) - Internal Factors - enzymes and proteins released by the cell

Regulation of Cell Division (cont) - apoptosis = programmed cell death Webbed Fingers

Apoptosis – Leaves in Fall

Incomplete Apoptosis

Cancer cells form tumors that may metastasize to other parts of the body Normal Cell Bloodstream A healthy cell may become a cancer cell if certain genes are damaged

Cancer cells form tumors that may metastasize to other parts of the body Cancer cells divide more often than do healthy cells and may form disorganized clumps called tumors

Cancer cells form tumors that may metastasize to other parts of the body Sometimes cancer cells break away from the tumor. They can be carried in the bloodstream to other parts of the body where they form new tumors.

According to the American Cancer Society, skin cancer is the most common of all cancers. This cancerous mole is an example of a skin cancer, which may metastasize quickly.

ABCD Rule (for moles, etc) Mnemonic to help remember what to look for A = Asymmetry (irregular shape) B = Border is irregular shape C= Color change (changing or many colors) D = Dimension (1/4 in or less) **other key signs to look for: New growth, changes in growth, painful feeling

Look for the ABCD Rule in this mole?

Why is sex with someone else better than sex by yourself?

Asexual Reproduction = reproduction of offspring from one parent - offspring are genetically identical to the parent …this is a BAD thing

Sexual Reproduction = reproduction of offspring from two parents - offspring are genetically different from the parents …this is a GOOD thing

Nut Disease in Squirrels Example Nut Disease in Squirrels

Some eukaryotic cells divide by mitosis

Some organisms can reproduce by asexual or sexual reproduction (depends on conditions)

Meiosis

Meiosis = cell reproduction that forms gametes (= sex cells = egg/sperm)

Meiosis (cont) - # of chromosomes is halved - produces haploid cells (23 chromosomes)

Meiosis (cont) Two Stages: Meiosis I Prophase I, Metaphase I, Anaphase I, Telophase I Meiosis II Prophase II, Metaphase II, Anaphase II, Telophase II

Meiosis (cont) Homologous chromosomes line up ( = tetrad) Portions of chromatids are exchanged ( = crossing over) - results in new mixture of genetic material ( = genetic recombination)

genetic recombination Meiosis (cont) tetrad crossing over genetic recombination

Meiosis (cont) Chromosomes separate randomly ( = law of independent assortment) - results in genetic variation

Meiosis (cont)

Spermatogenesis = production of sperm cells - makes 4 haploid cells called spermatids

Spermatogenesis

Oogenesis = production of egg cells - makes 1 haploid egg cell and 3 polar bodies - polar bodies degenerate

Oogenesis

Examples: Mitosis vs. Meiosis

Examples: Mitosis vs. Meiosis A human has 46 chromosomes - after mitosis, each body cell has 46 chromosomes - after meiosis, each sex cell (egg and sperm) has 23 chromosomes