CELL REPRODUCTION

Types of Cell Reproduction Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction Mitosis & binary fission are examples of asexual reproduction Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is an example Meiosis is an example

WHY DIVIDE? Multicellular organisms: –To repair or heal –To grow and develop –To replace cells that die Unicellular organisms: –To reproduce

NUCLEUS Contains genetic information (DNA) The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA moleculesThe instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules Normally, DNA is in the formed of long strands called chromatin.

During cell division, chromatin winds around proteins making more visible structures called chromosomes.

Chromosomes in Dividing Cells Each duplicated strand in a chromosome is called a chromatid & they are held together by the centromere Called Sister Chromatids

CELL CYCLE Most of the time cells are not dividing. Several proteins are involved in starting cell division. Some cells can divide in as little as 20 minutes.

Cells typically stop dividing when: – Nutrient levels drop (no food) –They come into contact with other cells (no room) –Receive chemical signals to stop.

Sketch the Cell Cycle Daughter Cells DNA Copied called Replication Cells Mature Cells prepare for Division Cell Divides into Identical cells

Some animations…. Cells Alive animation John Kyrk animation McGraw animation

INTERPHASE Cells spend most of their life in interphase. Normal cell activities occur. Chromosomes are not clearly visible. The chromatin looks like spaghetti.

To prepare for cell division, the chromosomes make copies of themselves. In other words, the DNA replicates.

CELL MEMBRANE Nucleus Cytoplasm For Your Sketch: Interphase

MITOSIS: CELL DIVISION FOR EUKARYOTES Four Stages 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase Remember: PMAT

PROPHASE Chromatin condenses and becomes visible as chromosomes. The nucleolus disintegrates. The nuclear membrane disintegrates.

Centrioles separate and move to opposite ends (poles) of the cell. Spindle fibers are made by the centrioles.

Animal Cell Plant Cell Photographs from: Spindle fibers Centrioles

Sister chromatids Spindle fibers For Your Sketch: Prophase the 1 st step in Mitosis

METAPHASE Chromatids attach to the spindle fibers The chromosomes line up at the middle of the cell (equator).

Animal Cell Plant Cell Photographs from:

Centrioles Spindle fibers For Your Sketch: Metaphase

ANAPHASE The joined chromatids separate and move to opposite ends of the cell. The chromatids move along the spindle fibers. In plant cells, the cell plate begins to form. Each pole (future daughter cells) now has an identical set of genes

Animal Cell Plant Cell Photographs from:

Centrioles Spindle fibers For Your Sketch: Anaphase

TELOPHASE The chromatids arrive at the opposite poles of the cell. Spindle fibers disintegrate. Two new nucleoli form New nuclear membranes form around the 2 new nuclei.

Individual chromosomes unravel and become chromatin again. Cytokinesis or the partitioning of the cell occurs (formation of cleavage).

Animal Cell Plant Cell Photographs from:

Nuclei Chromatin For Your Sketch: Telophase

Cytokinesis Means division of the cytoplasm Means division of the cytoplasm Division of cell into two, identical halves called daughter cells Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell In animal cells, cleavage furrow forms to split cell

Cytokinesis Cleavage furrow in animal cell Cell plate in animal cell

Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes. Sketch Cytokinesis

END RESULTS OF MITOSIS Two new “daughter” cells are made with each containing the same number and kinds of chromosomes as the original (parent) cell. They have the same genetic code: This means they are identical

BINARY FISSION: CELL DIVISION FOR PROKARYOTES (BACTERIA) The single chromosome attaches to the cell membrane. The DNA replicates making 2 identical chromosomes.

The cell elongates and eventually separates into 2 new cells. Each cell gets one chromosome.

CANCER Caused by uncontrollable cell division. Cells either fail to stop dividing or get signals to continue dividing. An increased number of cells makes a tumor. Tumors can be benign (non-cancerous) or malignant (cancerous). Cancer cells spread (metastasis) throughout body! Chemotherapy (anti-cancer drugs) kills cancer cells, but unfortunately it also damages healthy cells. This is why people get sick when they undergo chemotherapy.

Some Causes of Cancer Genetics Radiation Carcinogens Age Viruses and Bacteria Diet

Carcinogens Cancer causing agents –Ex. Cigarette smoke, pollution Can cause increased amounts of free radicals

Free Radicals Free radicals form when a weak bond splits between two molecules causing one of those molecules to lose an electron. (the molecules cannot function properly at this point) The free radical then attacks a different molecule to steal its electron, which causes more free radicals to form.

Free Radicals and antioxidants Free radicals can occur in your body naturally. Carcinogens can make free radicals in the body. Antioxidants battle free radicals by bonding with them before the free radicals can do any harm.

Fruits –Ex. berries, pomegranate, grapes, orange, plum, pineapples, kiwi, grapefruit Vegetables –Ex. cabbage, artichokes, Brussel sprouts, spinach, red beets Beans/ Legumes –Ex. soybeans, red kidney beans, coco beans Foods with High Antioxidants

More Foods with High Antioxidants Dry fruits –Ex. apricots, prunes, and dates Nuts and seeds –Ex. pecans, walnuts, hazelnuts, sunflower seeds Cereal –Ex. barley, millet, oats, corn