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  • Cells of the Immune System

    Cells of the Immune System

    Click & Learn

    An overview of the immune system, concentrating on the roles played by B and T lymphocytes, and the antigen-presentation system.

  • CTL killing a target cell

    CTL killing a target cell

    Clips

    (1 min 17 sec) Video microscopy of a cytotoxic T lymphocyte in action.

  • HIV life cycle

    HIV life cycle

    Animations

    (4 min 52 sec) How HIV infects a cell and replicates itself using reverse transcriptase and the host's cellular machinery.

  • Antigen presentation and CTL

    Antigen presentation and CTL

    Animations

    (2 min 34 sec) How a cell infected by a virus signals cytotoxic T lymphocytes to kill the cell before the virus replicates and spreads.

  • Protease inhibitors

    Protease inhibitors

    Animations

    (1 min 6 sec) Protease inhibitors prevent maturation of viral proteins inside HIV particles.

  • AZT blocks reverse transcriptase

    AZT blocks reverse transcriptase

    Animations

    (1 min 46 sec) HIV's reverse transcriptase mistakes AZT for thymidine. Once incorporated, AZT stops reverse transcription.

  • Classroom Activities: Planaria Regeneration Activity

    Classroom Activities: Planaria Regeneration Activity

    Activities

    This activity uses the planaria's property for regeneration and compares how long it takes for planaria cut in different places to regenerate a head. 

  • Classroom Activities: Stem Cells and Diabetes

    Classroom Activities: Stem Cells and Diabetes

    Activities

    To accompany the lecture series Potent Biology: Stem Cells, Cloning, and Regeneration.

  • Tissue Regeneration in Animals

    Tissue Regeneration in Animals

    Click & Learn

    An overview and comparison of different regenerative capabilities in many different organisms.

  • Planarian Regeneration and Stem Cells

    Planarian Regeneration and Stem Cells

    Scientists at Work

    (11 min 47 sec) A mini-documentary discussing the remarkable regenerative capabilities of the planarian, and how HHMI researcher Alejandro Sánchez Alvarado uses them to study the biology of stem cells.

  • Human Embryonic Development

    Human Embryonic Development

    Animations

    (2 min 18 sec) Human embryonic development depends on stem cells. During the course of development, cells divide, migrate, and specialize. Early in development, a group of cells called the inner cell mass (ICM) forms. These cells are able to produce all the tissues of the body. Later in development, during gastrulation, the three germ layers form, and most cells become more restricted in the types of cells that they can produce.

  • Differentiation and the Fate of Cells

    Differentiation and the Fate of Cells

    Animations

    (1 min 29 sec) As a human embryo develops, its cells become progressively restricted in the types of specialized cells that they can produce. Inner cell mass (ICM) cells of the blastocyst can make any type of body cell. Gastrula-stage cells can give rise to the cells of a given germ layer. Later, cells become even more restricted. For example, the pancreatic bud of the endoderm layer can only make the cells of the pancreas.

  • Creating Embryonic Stem Cell Lines

    Creating Embryonic Stem Cell Lines

    Animations

    (1 min 38 sec) The inner cell mass (ICM) cells of blastocyst-stage early human embryos can be removed and cultured. These cells can be grown in the lab indefinitely. Various growth factors cause these cells to develop into a variety of differentiated cells, such as muscle or nerve cells.

  • Somatic Cell Nuclear Transfer Animation

    Somatic Cell Nuclear Transfer Animation

    Animations

    (52 sec) Somatic cell nuclear transfer (SCNT) is a technique for cloning. The nucleus is removed from a healthy egg. This egg becomes the host for a nucleus that is transplanted from another cell, such as a skin cell. The resulting embryo can be used to generate embryonic stem cells with a genetic match to the nucleus donor (therapeutic cloning), or can be implanted into a surrogate mother to create a cloned individual, such as Dolly the sheep (reproductive cloning).

  • Zebrafish Heart Regeneration

    Zebrafish Heart Regeneration

    Animations

    (2 min 30 sec) The zebrafish heart is similar to the human heart in many respects. But unlike the human heart, the fish heart closes wounds rapidly and then regenerates to nearly full function. Fibroblast growth factor (FGF) is an important molecule in the regeneration process.

  • Fruit Fly Courtship

    Fruit Fly Courtship

    Clips

    (55 sec) Male courtship dances in two fruit fly species show that the wing spots play a prominent role.

  • Pitx1 Expression

    Pitx1 Expression

    Animations

    (55 sec) In the stickleback fish, pelvic-fin reduction resulted from changes in the regulatory switch elements of the Pitx1 gene. In the marine ancestor, the Pitx1 gene is activated in the pelvic-fin region during development to generate the fin. In the pelvic-reduced stickleback, the regulatory switch that normally turns on the Pitx1 gene is either missing or non-functional.

  • Fossil Record of Stickleback Evolution

    Fossil Record of Stickleback Evolution

    Clips

    (2 min 34 sec) A quarry site in Nevada carries the evolutionary history of a population of stickleback fish that resided there when it was a freshwater lake.

  • What Is Fat?

    What Is Fat?

    Posters

    The poster from the 2004 Holiday Lectures on Science, The Science of Fat. See how fat is stored and metabolized. (This poster is designed to printed at a maximum size of 29.5" x 23.5".)

  • How The Body Uses Fat

    How The Body Uses Fat

    Click & Learn

    This slide show explores some of the ways the body processes fat, including digestion, transport, conversion, and energy extraction.

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