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Cell Cycle Interactive Cell Reproduction 2.55 In most cases, a living thing grows because it produces more cells. Zygote blastula Early gastrula Late gastrula SURFACE-TO-VOLUME RATIO – Is greater in small cells than in larger cells – A greater surface area allows materials to enter and leave the cell at a faster rate DNA’s ability to produce enough messenger RNA decreases with an increase in cell growth Results in cell division – process whereby the cell divides into 2 daughter cells Rates differ from cell type to cell type Are affected by external conditions They have to be right Cells in certain places in the body, such as the heart and the nervous system rarely divide, if they divide at all. Cells of the skin and digestive tract grow and divide rapidly due to daily wear and tear. Cells grow until they come into contact with other cells. Cell growth and cell division are turned on and off to repair injuries. CANCER – is a disorder in which some cells have lost the ability to control their own rate of growth Cancer cells do not stop growing when they come in contact with other cells SKIN CANCER SKIN CANCER Are structures in the cell that contain the genetic information that is passed on from one generation of cells to the next. Are not visible in most cells except during mitosis. Contain the genetic information in the form of DNA Between cell divisions, chromatin forms condensed and dispersed regions During the early stages of mitosis, the chromatin condenses and the chromosomes become visible Chromatin is composed of DNA and protein After DNA replicates, the chromosomes become visible by condensing Sister chromatids – are two identical parts that result from DNA replication Are attached at an area called the centromere Cell cycle 1.50 Is the period from the beginning of one mitosis to the beginning of the next mitosis. Is the period when a cell grows, prepares for division, and divides to form 2 daughter cells which begin the cycle again The longest phase of an active cell cycle is Interphase. A period of nondivision Period of growth, development, replication, and synthesis Results in cell growth and development The chromosome number doubles Organelles and materials required for cell division are synthesized The nucleus synthesizes messenger RNA in order to direct cell activities 4.28 Interphase can be divided into three parts: G1 - S - G2. Mitosis or M-phase is the part of the cell cycle when the cell is actually dividing into two new daughter cells. Mitosis can be divided into four parts: Telophase Metaphase Prophase Anaphase 1.51 a period of active division Is the M phase Period when the nucleus divides into 2 nuclei The first phase of mitosis (is the longest) Chromosomes become visible as a result of the condensing and coiling of the chromatin The centrioles separate from each other and take up positions on the opposite sides (poles) of the nucleus The centrioles develop a spindle The spindle fibers help move the chromosomes apart The nucleolus disappears and the nuclear envelope breaks down Is the second phase of mitosis (shortest phase) Chromosomes line up across the center or equator of the cell Is the third phase of mitosis Centromeres that join the sister chromatids split causing the sister chromatids to separate and become individual chromosomes Chromosomes separate into 2 equal groups near the poles of the spindle Is the final phase of mitosis Chromosomes begin to unravel into a tangle of chromatin The nuclear envelope reforms around the chromatin The spindle begins to break apart, and a nucleolus becomes visible in each daughter nucleus Is the division of the cytoplasm into 2 individual cells In animal cells – the cell membrane moves inward until it pinches into nearly 2 equal parts, each part containing its own nucleus and cytoplasmic organelles Cleavage furrow Cell Plate In plant cells – a cell plate forms midway between the divided nuclei and gradually develops into a separating membrane in which a cell wall begins to appear Unicellular organisms – it is their method of reproduction 1 organism 2 organisms Multicellular organisms – in their body cells It is used to repair damaged tissue or replace cells and for growth Parent cell Daughter cells A KEGG PATHWAY (next slide) is a collection of manually drawn pathway maps representing the molecular interactions and reactions in the cell cycle for: 1. Metabolism - Carbohydrate, Energy, Lipid, Nucleotide, Amino Acids & More. 2. Genetic Information Processing 3. Environmental Information Processing 4. Cellular Processes 5. Human Diseases and 6. Drug Development KEGG: The Human Cell Cycle is regulated by many complex molecular interactions, reactions, and relations. In this course we have only covered the basics of the cell cycle. There is much more to learn and entire careers are made studying the cell cycle. A college degree in “Cell Biology” can be pursued at many Universities across the country. To see what jobs are available for a Cell Biologists check out the link below for current job offerings in the US: Cell Biologist Job Openings NOW THE END!