Binary Fission Time # of Bacterial Cells 20 40 60 (1hr) 80 100 120 140 20 40 60 (1hr) 80 100 120 140 160 180 (3hr) Bacteria double every 20 min in favorable conditions 0 min 20 min 40 min 60 min

Cell Cycle

Cell Growth and Cell Division Cell division is strictly controlled by specialized proteins in the nucleus. Your cells continue to divide as you continue to grow. Your body continues to replace cells that take a lot of wear and tear such as skin cells, stomach cells and intestinal cells. Cells such as muscle and nerve cells usually do NOT continue to divide in an adult, but continue to carry out functions necessary for survival

Cell Cycle: 3 Stages 1) Interphase - cells carry out the functions necessary for survival and cells that divide prepare for reproduction 2) Mitosis - divides the duplicated contents of the cell's nucleus into two equal parts 3)Cytokinesis - separates the two nuclei and cell contents into two daughter cells

http://www.youtube.com/watch?v=diXoAgH3LMk

Interphase Longest stage in the cell cycle. Cells carries out its various functions within the organism. Also, the cell roughly doubles everything in its cytoplasm Growth and Repair DNA Replication Continued Growth and Repair

Growth and Preparation (G1) The first phase of interphase, and a cell increases in size and makes the proteins and molecules necessary for the cell to survive. Some organelles begin to duplicate

Replication (S) DNA copies or makes a "replica" of itself by: 1) Enzymes separate the DNA by unwinding the double helix, then the steps of the DNA ladder break apart. http://www.youtube.com/watch?v=zdDkiRw1PdU

2) Each side then becomes a pattern or template on which a new side forms (remember A -T, and C-G) 3) results in two new DNA that have the same sequence of bases as the original DNA. (Identical genetic information)

Growth and Preparation (G2) After DNA replication, the cell continues to grow and makes materials such as proteins for the new cells. These cells are referred to as "daughter cells". The chromatin is loosely coiled to allow for production of proteins can be made in preparation for cell division. During this final phase of interphase important organelles such as mitochondria and chloroplasts are duplicated.

Mitosis -contents of a cell's nucleus divides -two daughter nuclei, each with the same number and kinds of chromosomes as the original cell -DNA molecules join together to from the sister chromatids of chromosomes, joined together by centromere.

Prophase - chromosomes coil up into a X-shape - nucleolus will disappear, and the nuclear membrane will begin to break down & eventually disappear -spindle fibres, tube-like structures made of protein -centrioles are organelles that "organize" spindle fibres. Centriols begin to move to opposite sides of the cell. -chromosomes attach to the spindle fibres at their centromeres

Metaphase -spindle fibres (now completely formed) pull the X-shaped chromosomes into a single line across the middle (or equator) of the cell.  

-once separate, each sister chromatid is considered to be a chromosome Anaphase -spindle fibres begin to pull the centromere apart, allowing the sister chromatids to move to opposite poles of the cell. -once separate, each sister chromatid is considered to be a chromosome

Telophase -spindle fibres begin to disappear -nuclear membrane forms around each set of chromosomes - Nucleolus appears within each nucleus - Chromosomes lengthen and get thinner *With two nuclei the cell is ready to divide http://www.youtube.com/watch?v=diXoAgH3LMk

Cytokinesis Final stage of a cell cycle: Separates the two nuclei into two daughter cells. The new cells are identical to the original parent cell. In animal cells, the cell membrane pinches together to divided the cells' cytoplasm and organelles. In plant cells, a cell plate forms along the centre of the cell to divide the cell (Cell Wall)  

The cell just divided to form two daughter cells.

Checkpoints in the cell cycle Activities during cell cycle are monitored and controlled at specific stages or checkpoints -proteins monitor cell and send information to nucleus. -Nucleus then instructs the cell whether or not to divide.

Cells will not divide if: There are not enough nutrients to support cell growth DNA within the nucleus has not been replicated c) DNA is damaged

If a mutation occus in a gene producing checkpoint protein the cell cycle control will be lost. As a result, a damaged cell may have uncontrolled cell division which is known as the disease, CANCER

Cancer KEY: Cancer cells have damage to their checkpoints, so regardless if their DNA is damaged, or if these cells begin to disrupt functions of nearby cells, cancer cells continue to divide and grow.

Example 1-Healthy cells grow in a single layer and stop dividing when they receive messages from neighboring cells. Cancer cells do not respond and grow in multiple layers disrupting the function of nearby cells.

Example 2: DNA is damaged, but continues to divide Example 2: DNA is damaged, but continues to divide. This results in damaged chromosomes which is shown by large, abnormal nuclei.

Example 3. Since DNA is damaged, they do not produce the proper protein for cell function, so a cancer cell formed in your lungs does NOT function as a lung cell

-Cancer cells can still receive nutrients from nearby blood vessels -Cancer cells can still receive nutrients from nearby blood vessels. So they continue to grow and divided even more rapidly to form tumors. - Cancer cells can spread to other areas of your body if tumor cells break away and are carried by the blood vessels to new locations.

Interphase G1: growth/development S: replication phase G2: continued growth/development Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

Daughter cell Sister chromatid Centromere Centriole Spindle fibers Checkpoint Cancer