Cell Growth Does an animal get larger because each cell increases in size or because it produces more of them? Mature red blood cells are not capable of dividing, as they do not possess nuclei. Therefore, it is not possible that red blood cells will divide as they travel along our blood vessels. New red blood cells are produced in the red bone marrow of long bones in adults, not from the cell division of mature red blood cells. "RBCs are terminally differentiated; that is, they can never divide. They live about 120 days and then are ingested by phagocytic cells in the liver and spleen."

Cell Growth As you might have guessed, living things grow by producing more cells. As you might have guessed, living things grow by producing more cells. The koalas have the same size cells, just one has more then the other. The koalas have the same size cells, just one has more then the other.

Why DO Cell’s Divide.. #1 reason is because as volume increases: #1 reason is because as volume increases: More demand is placed on cell’s DNA (DNA Overload) More difficult to bring in enough nutrients and get rid of waste (material exchange) #2 Ratio of surface area to volume. Before cell division the cell replicates all of its DNA. Before cell division the cell replicates all of its DNA.

Chromosomes In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by chromosomes. In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by chromosomes. The cells of every organism have a specific number of chromosomes. The cells of every organism have a specific number of chromosomes. Each chromosome consists of two identical “sister” chromatids. When the cell divides, the “sister” chromatids separate and go to each of the new cells. Each chromosome consists of two identical “sister” chromatids. When the cell divides, the “sister” chromatids separate and go to each of the new cells.

Chromosome Each pair of chromatids is attached at an area called a centromere. Each pair of chromatids is attached at an area called a centromere. Centromeres are usually located near the middle of the chromatids, although sometimes can be found at each end. Centromeres are usually located near the middle of the chromatids, although sometimes can be found at each end.

CELL CYCLE Mitosis is a process where cells are produced for growth and/or replacing damaged or old cells Mitosis is a process where cells are produced for growth and/or replacing damaged or old cells The process by which a cell reproduces to create two identical copies is known as mitosis. The process by which a cell reproduces to create two identical copies is known as mitosis. Cells formed by mitosis are known as daughter cells. Cells formed by mitosis are known as daughter cells. The cell division process occurs in several different stages, known collectively as the 'cell cycle'. The cell division process occurs in several different stages, known collectively as the 'cell cycle'. Many of the abnormal traits of cancer cells are due to defects in genes that control cell division. Many of the abnormal traits of cancer cells are due to defects in genes that control cell division.

Cell Cycle (phases) Interphase- cell resting (G1, S, G2) Interphase- cell resting (G1, S, G2) M Phase- Cell actively dividing (this occurs during Mitosis (M) or Cytokinesis, C) M Phase- Cell actively dividing (this occurs during Mitosis (M) or Cytokinesis, C)

Cell Cycle The cell cycle consists of four stages  G1, S, G2, and M and then cytokenesis. The cell cycle consists of four stages  G1, S, G2, and M and then cytokenesis. G1 and G2 are 'gap' phases. G1 and G2 are 'gap' phases. G1 phase (primary growth phase) –cell gets bigger G1 phase (primary growth phase) –cell gets bigger S in the synthesis phase in which the chromatin (DNA) is copied (replicated). S in the synthesis phase in which the chromatin (DNA) is copied (replicated). G2 (gap 2) –cell prepares to divide, organelles replicate G2 (gap 2) –cell prepares to divide, organelles replicate M is the mitotic phase in which the cell physically divides into two daughter cells. Has 4 sub- phases! M is the mitotic phase in which the cell physically divides into two daughter cells. Has 4 sub- phases! Most cells are NOT actively dividing. These cells are in a resting state (G). Most cells are NOT actively dividing. These cells are in a resting state (G).

Mitosis (M phase) steps which include the process for asexual cell division. Mitosis (M phase) steps which include the process for asexual cell division. Biologists divide the events of mitosis into four phases: Biologists divide the events of mitosis into four phases: - Prophase - Metaphase - Anaphase - Telophase Depending on the type of cell, the four phases may last anywhere from a few minutes to several days.

The kinetochore is the protein structure on chromosomes where the spindle fibers attach during cell division to pull the chromosomes apart. The kinetochore is the protein structure on chromosomes where the spindle fibers attach during cell division to pull the chromosomes apart. chromosomes spindle fibers chromosomes spindle fibers The kinetochore forms in eukaryotes, assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. The kinetochore forms in eukaryotes, assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. eukaryotescentromerechromosomemitotic spindle mitosismeiosis eukaryotescentromerechromosomemitotic spindle mitosismeiosis

PROPHASE The first and the longest phase of mitosis, prophase can take as much as 50 to 60 percent of the total time required to complete mitosis. The first and the longest phase of mitosis, prophase can take as much as 50 to 60 percent of the total time required to complete mitosis. Chromosomes condense, the nuclear membrane breaks down, and spindle fibers form, centrioles move to opposite ends. Chromosomes condense, the nuclear membrane breaks down, and spindle fibers form, centrioles move to opposite ends.

METAPHASE The replicated chromosomes line up in the middle of the cell The replicated chromosomes line up in the middle of the cell Chromosomes attach to spindle fibers Chromosomes attach to spindle fibers

ANAPHASE Chromosomes separate at the centromere and the cell becomes elongated, with distinct ends (poles). Chromosomes separate at the centromere and the cell becomes elongated, with distinct ends (poles).

TELOPHASE Chromosomes gather at opposite ends and start to unwind Chromosomes gather at opposite ends and start to unwind Spindles break down Spindles break down Nuclear envelopes re- form at the two poles and new cell membranes begin to form to create two independent cells Nuclear envelopes re- form at the two poles and new cell membranes begin to form to create two independent cells

CYTOKINESIS the division of the cytoplasm to make two complete daughter cells ANIMAL CELLS ANIMAL CELLS Cell membrane pinches apart into two equal parts with one nucleus in each daughter cell Cell membrane pinches apart into two equal parts with one nucleus in each daughter cell PLANT CELLS PLANT CELLS Cell plate forms between two nuclei Cell plate forms between two nuclei Cell plate develops into a cell wall Cell plate develops into a cell wall

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Activity Pass out white boards to students (groups of 2-3) Pass out white boards to students (groups of 2-3) Flip through the following slides and have students either draw or label the picture Flip through the following slides and have students either draw or label the picture

CYTOKINESIS

METAPHASE

PROPHASE

ANAPHASE

Cell Cycle Regulators Scientists discovered that cells in mitosis contain a protein called cyclin when injected in a non-dividing cell, would cause a miotic spindle to form. Scientists discovered that cells in mitosis contain a protein called cyclin when injected in a non-dividing cell, would cause a miotic spindle to form. Cyclins regulate the timing of the cell cycle in eukaryotic cells. Cyclins regulate the timing of the cell cycle in eukaryotic cells.

Uncontrolled Cell Growth Why is cell growth regulated so carefully? Why is cell growth regulated so carefully? Cancer- a disorder in which some of the body’s own cells lose the ability to control division. Cancer cells do not respond to the signals that regulate the division of most cells. Cancer- a disorder in which some of the body’s own cells lose the ability to control division. Cancer cells do not respond to the signals that regulate the division of most cells.