Lesson Overview

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Lesson Overview

• 10.3 Regulating the Cell Cycle

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The Cell Cycle

• The controls on cell growth and division can be
  turned on and off.
• For example, when an injury such as a broken
  bone occurs, cells are stimulated to divide
  rapidly and start the healing process. The rate
  of cell division slows when the healing process
  nears completion.

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The Discovery of Cyclins

• 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.

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Regulatory Proteins

• 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.

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HeLa Cells

• The Story of Henrietta Lacks http//www.youtube.co
  m/watch?v0gF8bCE4wqAfeaturerelated

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Apoptosis

• 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. For example, the foot of a mouse is
  shaped the way it is partly because the toes
  undergo apoptosis during tissue development.

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Cancer and the Cell Cycle

• Cancer is a disorder in which body cells lose
  the ability to control cell growth.
• Cancer cells divide uncontrollably to form a
  mass of cells called a tumor.

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Cancer and the Cell Cycle
A benign tumor is noncancerous. It does not
spread to surrounding healthy tissue. A
malignant tumor is cancerous. It invades and
destroys surrounding healthy tissue and can
spread to other parts of the body. The spread of
cancer cells is called metastasis. Cancer cells
absorb nutrients needed by other cells, block
nerve connections, and prevent organs from
functioning.
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What Causes Cancer?

• 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.
• A damaged or defective p53 gene is common in
  cancer cells. It causes cells to lose the
  information needed to respond to growth signals.

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Treatments for 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.
• Cancer Warrior PBS

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From One Cell to Many

• All organisms start life as just one cell.
• Most multicellular organisms pass through an
  early stage of development called an embryo,
  which gradually develops into an adult organism.
• During development, an organisms cells become
  more differentiated and specialized for
  particular functions.

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Defining Differentiation

• The process by which cells become specialized is
  known as differentiation.
• During development, cells differentiate into
  many different types and become specialized to
  perform certain tasks.

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Human Development

• Biologists say that such a cell is totipotent,
  literally able to do everything, to form all the
  tissues of the body. (a fertilized egg)
• After about four days of development, a human
  embryo forms into a blastocyst, a hollow ball of
  cells with a cluster of cells inside known as the
  inner cell mass.
• The cells of the inner cell mass are said to be
  pluripotent, which means that they are capable of
  developing into many, but not all, of the body's
  cell types.

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Stem Cells

• Stem cells are unspecialized cells from which
  differentiated cells develop.

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Embryonic Stem Cells

• Embryonic stem cells are found in the inner
  cells mass of the early embryo.
• Embryonic stem cells are pluripotent.
• Researchers have grown stem cells isolated from
  human embryos in culture. Their experiments
  confirmed that embryonic stem cells have the
  capacity to produce most cell types in the human
  body.

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Adult Stem Cells

• Adult organisms contain some types of stem
  cells. Adult stem cells are multipotent. They can
  produce many types of differentiated cells.
• Adult stem cells of a given organ or tissue
  typically produce only the types of cells that
  are unique to that tissue.

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Potential Benefits

• Stem cell research may lead to new ways to
  repair the cellular damage that results from
  heart attack, stroke, and spinal cord injuries.

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Ethical Issues

• Most techniques for harvesting, or gathering,
  embryonic stem cells cause destruction of the
  embryo.
• Government funding of embryonic stem cell
  research is an important political issue.
• Groups seeking to protect embryos oppose such
  research as unethical. Other groups support this
  research as essential to saving human lives and
  so view it as unethical to restrict the research.
• BBC Documentary