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BIOLOGY 1110 PRINCIPLES OF BIOLOGY Biology 1110 Laboratory # 9 The Cell Cycle and Mitosis Support/Review Materials All of the micrographs in this presentation were photographed in the Mn. West Biology laboratory unless otherwise noted. The microscope symbol that you see indicates power. A left mouse click on the microscope viewing magnification. Give it a try. a change in microscope most often increases the
The Cycle of a Dividing Cell The object of the cell cycle is to produce two “daughter” cells from the single “mother” cell. DNA, the genetic material, contains all of the instructions to run the cell. The necessity of DNA duplication during interphase should be obvious.
The Cycle of a Dividing Cell Mitosis takes up about 10% of a typical cell cycle. Through the phases of mitosis the cell’s nucleus divides to form the two “daughter” nuclei. With the two “daughter “ nuclei formed, the cell is ready to separate into two separate cells.
The Cycle of a Dividing Cell The mitotic phases accomplish the nuclear division. They are: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase We will study interpase and the mitotic phases in both animal and plant dividing cells.
Interphase and Mitosis in the Whitefish Blastula The two low power micrographs below are whitefish blastulas. A blastula is an early stage an embryo consisting of many cells. Growth of the embryo involves rapid cell cycles that can be readily studied microscopically.
Cell Cycle Whitefish Blastula These two low power micrographs contain numerous cells in the interphase (see )of the cell cycle. During the interphase the nuclear membrane is present and the nuclear content consists of the granular chromatin. The chromatin contains the DNA (genetic material) that must be duplicated. Let’s take a closer look
Inter. Phase The nucleus is intact, surrounded by a nuclear membrane. The granular chromatin is clearly visible. It is this chromatin that will give rise to the chromosomes as we move into the mitosis.
Mitosis – The Division of the Nucleus � Remember that the purpose of the mitosis is to produce the two “daughter” nuclei. � The division of the nucleus is accomplished through the four mitotic phases. They are: � 1. Prophase � 2. Metaphase 3. Anaphase 4. Telophase
The Cycle of a Dividing Cell The typical dividing cell spends about 90% of its time in a period called interphase. During the interphase, the cell is growing, carrying out its normal metabolic functions, duplicating its DNA, and getting ready for the next division.
Mitosis – Prophase Events The major events of the prophase include the following: - the nuclear membrane disintegrates. - the chromatin condenses (wraps up) forming the chromosomes. - the mitotic spindle begins to form. Let’s take a closer look
Prophase of Mitosis � The high power micrograph demonstrates two cells in prophase. � The chromatin is condensing, giving rise to the rod-like chromosomes. � The chromosomes are deeply stained and clearly visible.
Metaphase of Mitosis After the prophase the cell moves into the metaphase. In the metaphase the chromosomes lineup at the midplane of the cell. Metaphase The chromosomes are contained within the mitotic spindle. The fibers of the mitotic spindle are clearly evident in both micrographs. Let’s take a closer look
Metaphase in an animal cell � � On high power we clearly see the lined up chromosomes contained within the mitotic spindle. The spindle fiber attach to the chromosomes Mitotic spindle
Metaphase in an animal cell In this metaphase diagram we can see the chromosomes lined up within the mitotic spindle. We also note that the a spindle fiber attaches to each chromosome from each direction. Note that each chromosome consists of two identical chromatids (“sister” chromatids). From this we understand that the cell contains two full sets of genetic instructions.
Anaphase of Mitosis As the cell enters the anaphase of mitosis, the two chromatids of each chromosomes begin to separate. The spindle fibers begin to retract and pull the chromatids (chromosomes) towards each pole of the cell. The separation of anaphase separates the two identical sets of DNA; the two identical sets of instructions. Anaphase
Anaphase in an Animal Cell The anaphase diagram clearly shows the separation of chromatids. The spindle fibers pull the two sets of genetic instruction apart. The formation of the two “daughter” nuclei is well underway. Direction of movement
Telophase of Mitosis Telophase is the last phase of mitosis. The mitotic spindle has finished its job and disintegrates. The two daughter nuclei are forming. The cell will separate into the two “daughter” cells. Go to high power
Telophase in an Animal Cell Both of these animal cells have taken on the shape of the number 8 Note the cleavage furrow (constriction) at the pointer. This constriction will continue until the two “daughter” cells separate.
Telophase in an Animal Cell The illustration demonstrates the major events of the telophase. The mitotic spindle disintegrates. The two “daughter” nuclei are forming. The “mother” cell is dividing to produce the two “daughter” cells. This division is called the cytokinesis. “daughter” nuclei forming spindle
Interphase and Mitosis in Dividing Plant Cells You may remember from a previous lab that plant meristems are tissues where rapid cell division supports primary growth. Meristematic tissue is found in stem tips and root tips. We are going to study dividing cells in the Allium (onion) root tip Let’s take a high power look at this root tip.
Interphase in a Plant Cell Take a look at this interphase cell. The black arrow is pointing to the plant cell wall. The red arrow is pointing at the nucleus. Within the membraneenclosed nucleus we see the grainy chromatin material.
Prophase in the Plant Cell You can see the chromatin starting to condense to form chromosomes in these early prophase cells. Can you find a third prophase cell in the micrograph? There also many interphase cells for you to look at. You will see quite a similarity to the events of the animal cell cycle.
Prophase in the Plant Cell Later in prophase the rodlike forming chromosomes become much more apparent.
Late Prophase Later in the prophase, the chromatin codensation , forming the rod-like chromosomes is well demonstrated. Forming Chromosomes
Metaphase in the Plant Cell Like in the animal cell, the metaphase chromosomes line up at the midplane. Remember that each chromosomes contains two sets of genetic instructions.
Anaphase in the Plant Cell The separation of the two chromosomes groups (two sets of instructions)can be clearly seen in the identified cells. The formation of the two “daughter “ nuclei is well under way.
Telophase in the Plant Cell Cytokinesis (division of the cell) is occurring in the identified plant cells. The rigid plant cell wall prevents the type of division we saw in animal cells.
Telophase in the Plant Cell The “daughter” cells are formed as first a cell plate and then new cell wall forms between the “daughter” nuclei. The cycle is complete. Daughter Nuclei Cell Plate
Plant Cell Practice You should be able to find all studied stages and phases in the micrographs below.
Models – Animal Cell Cycle Interphase. Note the distinct nucleus. The granular chromatin is present in the nucleus.
Prophase Early Prophase. The chromosomes are starting to form from the chromatin. Later Prophase. Chromosomes almost fully formed. Mitotic spindle is developing
Metaphase The fully formed metaphase chromosomes line up at the midplane of the spindle. Late metaphase; early anaphase.
Anaphase The separation of the chromosome groups is starting. This anaphase model shows clear separation of the two chromosome groups.
Early and Late Telophase Cytokinesis (cell division) nearly complete “Daughter” nuclei forming Spindle disintegrates Two “daughter” cells entering the next interphase
T e h d n E
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