Chapter 10 Cell Cycle - Mitosis
WHAT CELL REPRODUCTION ACCOMPLISHES Cell division plays important roles in the lives of organisms. Cell division replaces damaged or lost cells permits growth allows for reproduction
Cells come from Cells The Cell Theory living things grow by producing more cells cells do not normally become bigger because there would be more demands placed on the cell and the cell would have to expend more energy to maintain itself. When a cell undergoes reproduction, or cell division, two daughter cells are produced that are genetically identical to each other to the parent cell.
Cell Division In asexual reproduction, single-celled organisms reproduce by simple cell division there is no fertilization of an egg by a sperm.
Division of the Cell Cell division replaces damaged or lost cells permits growth allows for reproduction Before cell division occurs, the cell replicates all of its DNA so that each daughter cell gets the same genetic information as the parent cell
Result of DNA replication
Chromosomes When the cell divides, the sister chromatids of a duplicated chromosome separate from each other. Once separated, each chromatid goes to each of the 2 new cells and is considered a full-fledged chromosome identical to the original chromosome.
Figure 8.UN01 Duplication of all chromosomes Distribution via mitosis Genetically identical daughter cells
The Cell Cycle The cell cycle series of events that cells go through as they grow and divide. during the cell cycle a cell grows, prepares for division and divides to form 2 daughter cells, each of which begins the cycle again. The cell cycle consists of two distinct phases: 1. interphase in-between period of growth 2. the mitotic phase cell division
The Cell Cycle - Interphase Most of a cell cycle is spent in interphase. During interphase a cell performs its normal functions Replicates all of its DNA sister chromatids doubles everything in its cytoplasm grows in size
The Cell Cycle - Interphase Interphase can be broken down into 3 distinct phases 1. G1 phase cells increase in size, make new proteins and organelles 2. S phase chromosomes replicate, DNA synthesis 3. G2 phase completion of organelle production
The Cell Cycle The mitotic (M) phase includes two overlapping processes: 1. mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei 2. cytokinesis, in which the cytoplasm is divided in two
Mitosis Mitosis consists of four distinct phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase
Mitosis 1. Prophase Chromosomes condense and coil more tightly and are visible through a light microscope. Centrioles separate and move to opposite ends of the nucleus. The spindle, which consists of microtubules structures begins to form from the centrioles. Chromosomes become attached to the spindle fibers at the centromere. Nuclear envelope breaks down.
Mitosis 2. Metaphase Mitotic spindle is fully formed Chromosomes line up between the two poles of the spindle (between the two centrosomes) Microtubules attached to the centromeres play tug of war keeping the chromosomes in the middle of the cell.
Mitosis 3. Anaphase Sister chromatids separate and move toward opposite poles of the cell as the spindle microtubules shorten Microtubules not attached to chromosomes get longer and elongate the cell.
Mitosis 4. Telophase Chromosomes have reached the opposite ends of the cell Nuclear envelopes forms Chromosomes uncoil Spindle dissapears
Mitosis Cytokinesis usually begins during telophase, divides the cytoplasm is different in plant and animal cells.
Cytokinesis In animal cells, cytokinesis is known as cleavage begins with the appearance of a cleavage furrow, an indentation at the equator of the cell.
Cytokinesis In plant cells, cytokinesis begins when vesicles containing cell wall material collect at the middle of the cell and then fuse, forming a membranous disk called the cell plate.
Regulating the Cell Cycle Certain cells in the body do not divide at all once they are formed such as muscle cells nerve cells Other cells grow and divide rapidly such as skin bone marrow blood
Controls on Cell Division Normal plant and animal cells have a cell cycle control system that consists of specialized proteins called cyclins, which send stop and go-ahead signals at certain key points during the cell cycle.
Uncontrolled Cell Growth When cells lose the ability to control growth the consequences can be severe. Cancer is a disorder in which cells lose the ability to regulate cell division. Cancer cells do not respond to the signals that regulate the growth of most cells. Cancer cells divide rapidly and form tumors which can be benign or malignant.
What Is Cancer? The spread of cancer cells beyond their original site of origin is metastasis. Malignant tumors can spread to other parts of the body and interrupt normal body functions. A person with a malignant tumor is said to have cancer.
Figure 8.9 Lymph vessels Tumor Blood vessel A tumor grows from a single cancer cell. Glandular tissue Cancer cells invade neighboring tissue. Metastasis: Cancer cells spread through lymph and blood vessels to other parts of the body.
Cancer Prevention and Survival Certain behaviors can decrease the risk of cancer: not smoking exercising adequately avoiding exposure to the sun eating a high-fiber, low-fat diet performing self-exams regularly visiting a doctor to identify tumors early