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Transcript
Class Notes Cellular Reproduction Chapter 9: p. 244-257 And Inside the Cell p. 48-51 Questions/Main Idea: Why is there a limit on cell size? What is the cell cycle? Name: _______________________________________ Period:_______________________________________ Date: _______________________________________ Notes: The ratio of surface area (cell membrane) to volume (cytoplasm and organelles) is important. In small cells, it is easier for nutrients and waste products to move to their appropriate location. In larger cells, there would be difficulty supplying necessary substances throughout the cell, and transporting substances throughout the cell. (ex. Is it easier for a ping pong ball to move across a bucket of water or a swimming pool?) Define the 3 main phases of the cell cycle: Interphase- Cell grows, carries out cell functions, replicates (copies) DNA Mitosis – Cell’s nucleus and nuclear material divides Cytokinesis - The cell’s cytoplasm divides, creating a new cell What happens during Interphase? G1 – period immediately after a cell divides. The cell grows and carries out normal cell functions, preparing for DNA replication S - Synthesis – Cell copies its DNA in preparation for cell division (“Replication”) G2 – Cell prepares for the division of its nucleus. Proteins that make microtubules for cell division are made, and the cell checks itself to make sure it’s ready to continue the next stage of division (ex. replicated DNA is checked for errors) What is the difference between chromosomes and chromatin? What is the name of the method prokaryotic cells use to divide? Define sister chromatid and centromeres: Chromosomes – Condensed form of DNA, the genetic material that is passed from generation to generation of cells. Chromatin- Relaxed form of DNA during interphase, which allows for DNA to replicate Binary Fission Sister chromatid- each half of the X-shaped chromosome is an identical copy of that chromosome’s DNA. Centromere- the structure at the center where the sister chromatids are attached For each of the following stages of mitosis, describe what happens, and draw a diagram: PROPHASE In prophase, the longest stage of mitosis: chromatin condenses into X-shaped chromosomes (containing 2 identical sister chromatids). The nucleolus disappears. The nuclear membrane disintegrates and the The spindle apparatus begins to form. The spindle apparatus includes spindle fibers, centrioles (in animal cells), and aster fibers. The spindle apparatus is important in moving chromosomes, to ensure that each new cell receives a complete copy of the DNA. METAPHASE In metaphase, one of the shortest phases of mitosis: Sister chromatids are pulled by motor proteins along the spindle apparatus towards the middle of the cell Sister chromatids line up along the equator ANAPHASE In anaphase, the chromatids are pulled apart: The microtubules of the spindle apparatus shorten, which pulls at the centromere of each sister chromatid, causing them to separate into 2 identical chromosomes. The chromosomes move toward the poles of the cell (opposite sides) TELOPHASE The last stage of mitosis is telophase. Chromosomes arrive at the poles and begin to relax or deconsense 2 new nuclear membranes begin to form Nucleoli reappear Spindle apparatus breaks down and parts are recycled to build the cytoskeleton Nucleus has divided, but cell division is not yet complete CYTOKINESIS Cytoplasm and all other cell contents divide, resulting in 2 identical cells How does a cell regulate its cycle? How is cancer a result of an uncontrolled cell cycle? What are carcinogens? What is Apoptosis? What are stem cells? Unspecialized cells that can develop into specialized cells Proteins (cyclins and CDKs) regulate the cell cycle by controlling the start and end of various activities within the cell Quality control checkpoints monitor the cycle and can stop it if something goes wrong. Ex. Check DNA for mistakes before replication, check for mistakes after replication Cancer is uncontrolled growth and division of cells – a failure in the regulation of the cell cycle. Cancer cells can crowd out normal cells Carcinogens are agents that are known to cause cancer Apoptosis is programmed cell death Examples: cells between fingers and toes during development of hands and feet cells in the leaves that fall in autumn Damaged cells (like sunburned skin) Embryonic Stem Cells – after a sperm fertilizes an egg, the cells divide repeatedly until there about 150 cells which have not become specialized yet. Each can develop into many various types of cells. Embryonic stem cell research is controversial because of ethical concerns about the source of the cells. Adult Stem Cells – found in various tissues, might be used to repair the same kind of tissue in which they are found. They might be able to develop into different types of cells, or used in treatments of diseases. Less controversial because the cells can be obtained with the consent of their donors. Additional notes or interesting facts you learned: Additional questions you still have: