 Stem Cells Regenerate New Finger!

 Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division.

 Before dividing, each cell must pass on genetic information to each new cell.  The production of genetically identical offspring from a single parent is known as asexual reproduction.  Offspring produced by sexual reproduction inherit some of their genetic information from each parent.

 Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are genetically identical to the single cell that produced them.  Asexual reproduction is a simple, efficient, and effective way for an organism to produce a large number of offspring.  Both prokaryotic and eukaryotic single- celled organisms and many multicellular organisms can reproduce asexually.

 In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow.  The offspring produced inherit some genetic information from both parents.

 The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.  Every cell must copy its genetic information before cell division begins.  Each daughter cell gets its own copy of that genetic information.

Is the picture below an example of asexual reproduction or sexual reproduction? Explain your answer using the word parent.

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 During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

 The eukaryotic cell cycle consists of four phases: G1, S, G2, and M.  Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.

 In the G1 phase, cells increase in size and synthesize new proteins and organelles.

 In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

 In the G2 phase, many of the organelles and molecules required for cell division are produced.  Ex. Spindle Fiber

 In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.  Mitosis is the division of the cell nucleus.  Cytokinesis is the division of the cytoplasm.

 Chromatid – each strand of a duplicated chromosome  Centromere – the area where each pair of chromatids is joined  Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle  Spindle – a fanlike microtubule structure that helps separate the chromatids

 During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.  The centrioles move to opposite sides of nucleus and help organize the spindle.  The nucleolus disappears and nuclear envelope breaks down.

 During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.  The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

 During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.

 During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.  A nuclear envelope re-forms around each cluster of chromosomes.  The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.

 Cytokinesis is the division of the cytoplasm.  Cytokinesis completes the process of cell division – it splits one cell into two.  In plants, a cell wall then forms in between the two new membranes.

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 The cell cycle is controlled by regulatory proteins both inside and outside the cell.  The controls on cell growth and division can be turned on and off.

 Internal regulators are proteins that respond to events inside a cell. They allow the cell cycle to proceed only once certain processes have happened inside the cell.  External regulators are proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle.  Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.

 Cyclins are a family of proteins that regulate the timing of the cell cycle in eukaryotic cells. This graph shows how cyclin levels change throughout the cell cycle in fertilized clam eggs.

 Apoptosis is a process of programmed cell death.  Apoptosis plays a role in development by shaping the structure of tissues and organs in plants and animals.

 Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.  Cancer cells divide uncontrollably to form a mass of cells called a tumor. A benign tumor is noncancerous. A malignant tumor is cancerous The spread of cancer cells is called metastasis.

 Cancers are caused by defects in genes that regulate cell growth and division.  Some sources of gene defects are smoking tobacco, radiation exposure, defective genes, and viral infection.

 P53: Tumor Suppressor Genes  BRCA1: Breast Cancer  Her2/Neu: Ovarian Cancer  APC: Colon Cancer

 Some localized tumors can be removed by surgery.  Many tumors can be treated with targeted radiation.  Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

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