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SCIENCE 9 ~~Asexual Reproduction – Mitosis NOTES~~ NAME: ______________ DATE:_______________ CLASS: 90__ Asexual Reproduction • Asexual reproduction requires _________________ • The offspring produced are _________ to the parent. • Asexual reproduction occurs in our ___________cells. This means all of our cells except for sperm cells in males and egg cells in females. We need asexual reproduction for three reasons: • __________ We grow from one initial cell to an adult. • __________ When we injure ourselves, our cells must reproduce asexually to replace this. • __________ Our cells are constantly being replaced. Most of our cells have a very short life span. Why do our cells need to be replaced? Our cells don’t live for ever! Some are programmed to die (PCD-Programmed Cell Death). Some cells die when they are _________________________. Some cells die when they don’t receive enough ___________________. These cells need to be replaced for our bodies to continue to function! _____________ cells die every minute in your body!!! Our cells have varying life spans. Why do we age? • Asexual Reproduction/Mitosis! • As we just stated-our cells are ____________________. As we age, they are either ______________, or are replaced _____________. When our cells stop replacing themselves at a fast pace, our skin wrinkles, our bones become weak, and we our immune system is weakened. Cancer-Mitosis gone bad! • Our cells are ____________________ when something goes wrong, but cancerous cells cannot do this. • When cells divide at an uncontrollably fast rate, cancer is created. • The cancerous cells _____________, and _________ the good cells of oxygen and food. • The risk of cancer is increased by tobacco, radioactivity, UV radiation, etc The First Cell • The first cell of a new organism is called the zygote. • It is created by the fusion of the __________________________. • This cell will divide into two, these two cells will each divide into two more (four total cells) and so on to create the new organism. • Each of these cells must contain ____________________. Maintaining Identical DNA: • If cells simply divided into two, there would be only a fraction of the original nucleus (and therefore original DNA) in each cell. • To ensure that each cell has an entire set of chromosomes, each of our cells goes through what is called “_________________” each time they divide. The Cell Cycle The Cell cycle allows the cell time to under go the process of______________________ (mitosis + cytokinesis), and _____________________ The majority of a cells life is spent in the ___________ and growth portions of its cycle. Before we begin, some terminology… • Genetic material, called DNA, is found on the ________________ located in the nucleus of a cell. • The genetic material that makes up chromosomes is called ______________. • When the chromatid is duplicated, the two ___________________ are attached in the middle by a ________________. Getting Ready – ________________ • The period _______________ is called interphase. • During this period, the cell grows and the genetic material (called chromatid) duplicates The duplicated sister chromatids attach in the middle by a _______________ to create a double stranded chromosome. • This process ensures that the same genetic information is passed on to each of the two new daughter cells. Mitosis Phase #1- _____________ During prophase: • The double-stranded chromosomes _____________ (shorten and thicken) • The _________________ (the membrane surrounding the nucleus) dissolves. • The ______________ move to opposite poles of the cell • The ________________ begin to form from the centrioles • Spindle fibers attach to opposite ends of the ________________ Phase #2- ___________ During metaphase: • The spindle fibers tug on opposite sides of the ___________ • This tugging action causes the double-stranded chromosomes to form a _________________ at the ___________ of the cell. This “equator” is called the _____________. Phase #3-____________ During Anaphase: • The spindle fibers ___________________. • This causes the _____________ to split in two. • One _______________ moves towards each pole of the cell. • If this process is successful, each daughter cell will have a complete set of identical genetic information. Phase #4- _____________ During Telophase: • The spindle fibers continue to shorten, pulling the sister chromatids all the way to _____________________. • The spindle fibers begin to _____________. • The _________________ form around each set of single-stranded chromosomes. • The chromosomes begin to uncoil into thin strands of chromatid. Wrapping up - Cytokinesis: • Cytokinesis happens after mitosis. During cytokinesis: • Animal cells: The ____________ pinches off near the middle of the cell, dividing the _______________ into two new cells. • Plant cells: A ______________ develops across the centre of the cells, forming a new ______________ and two new cells.