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Mitosis. To err is human to divide is divine. Why is Mitosis so important??. Mitosis means the exact copying of cells. Technically it means division of the nucleus. In biology we tend to refer to mitosis as making exact copies and then meiosis as making sex cells.
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Mitosis To err is human to divide is divine
Why is Mitosis so important?? • Mitosis means the exact copying of cells. • Technically it means division of the nucleus. • In biology we tend to refer to mitosis as making exact copies and then meiosis as making sex cells. • When you were born it was mitosis that helped you grow from a fertilized egg to an adult. • This toddler is learning to walk.
Regeneration • The lizard lost its tail to a predator. • It will grow a new tail through mitosis.
Fission • This Sea Anemone is reproducing by fission. • It splits in half and grows new parts through mitosis.
Healing • For the body to heal, the process of mitosis replaces damaged cells with new, healthy cells. • This broken bone will need lots of mitosis in order for it to heal properly. • Which bone is this?
Exact copies • The purpose of mitosis is to make exact copies of cells. • You start from one cell and you end up being composed of billions. • Each of those cells, genetically, is like the others. • These identical twins came from one fertilized egg.
Diplois vs. Haploid • An organism or cell that is haploid has one copy of its DNA. • In Eukaryotic cells our DNA is organized into what are called chromosomes or linear stretches of DNA. • For the haploid cell it would have one copy of each of its three chromosomes. • This one copy would be the haploid or (N) • For the top set of chromosomes N = 3
Diploid • A diploid cell is going to have 2 copies of each chromosome. • So, it will have 2 copies of chromosome 1 and 2 copies of chromosome 2, and 2 copies of chromosome 3.. • So, for the lower diagram 2N = 6
For humans • For humans a sperm or an egg are each haploid. N • They each have just one copy of each chromosome. • For people that would be 23 chromosomes. • When the egg is fertilized the zygote has two copies of each chromosome. • This would be 46 chromosomes. (2N) • This picture shows the human chromosome pairs. • What is special about the X and Y chromosome?
Inheritance and genes • Each chromosome has thousands of genes. • You get one chromosome from your dad and one from your mom. • Every cell in your body, except the sex cells, has two copies of each chromosome. • If you are a boy who gave you your Y chromosome?
The Cell Cycle • The cell cycle is how cells go from one cell to two. • The cell cycle is a lot like a copy machine. • Once it starts it just keeps making copy after copy after copy. • Most of the time the cell is getting ready to go into mitosis. • It is in interphase. (I) • What are the three division of interphase?
G1 (gap) phase • The first phase in interphase that a new cell enters is the G1 (gap) phase. • A good way to think of the G phase is that it stands for grow. • Because that is what the cell is going to do. • A cell in the G1 phase is getting larger and larger. • As this cell gets larger what happens to the surface area to volume ratio?
S Phase • The next phase of interphase is the S phase. • In this phase the cell is making copies of its DNA. • In this phase DNA replication is going on. • By the time we get to the end of the S phase all the DNA in a cell has been replicated. • Why is it important that there are two copies of the cells DNA?
G 2 phase • In the G 2 phase the cell continues to grow. • In summary, in G 1 the cell grows. • In S the cell copies its DNA. • In G 2 the cell continues to grow. • By the time the cell is through those three stages of interphase it is ready to divide.
Cells that do not divide • Some cells do not undergo mitosis. • Examples of these cells include nerve cells of the brain and spinal cord and muscle cells. • These cells remain in what is termed the G 0 phase.
Chromosome structure • This is what a chromosome looks like after the S phase. • It has now made a copy of itself. • Each side would be called a chromatid. (1) • The two sides are identical to each other. • (2) is the location of the centromere. • 3 is the short arm and 4 is the long arm. • What is the name of the chromosomes before they appear at the end of the S phase?
Cancer • Cancer are cells that reproduce wildly producing non-functioning tissue. • It is mitosis run amuck. • These cells could migrate throughout the body growing wherever they land.
Tumor • A group of cancer cells growing in one place. • These cells secrete chemicals that cause the body to make blood cells to feed the growing tumor. • Pieces from the tumor can break off and lodge in another part of the body and grow there (metastasis)
