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Showing 161-180 of 206 Resources
  • HIV life cycle

    HIV life cycle


    (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


    (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


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

  • AZT blocks reverse transcriptase

    AZT blocks reverse transcriptase


    (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

    Labs & Demos

    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. 

  • 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


    (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


    (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


    (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


    (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


    (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


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

  • Pitx1 Expression

    Pitx1 Expression


    (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


    (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.

  • 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.

  • Molecular Structure of Fat

    Molecular Structure of Fat

    Click & Learn

    This slide show delves into the various molecular shapes that fat can take.

  • Pima Indians

    Pima Indians


    (2 min 36 sec) A clip about the Pima Indian tribe and how environment has affected them.

  • Leptin Feedback Control System

    Leptin Feedback Control System


    (1 min 1 sec) Demonstrates how changes in the amount of fat tissue lead to changes in leptin levels and thus changes in appetite.

  • How a Heart Attack Occurs

    How a Heart Attack Occurs


    (37 sec) A 3-D animation that shows how plaques form in a blood vessel, leading to blockage and a heart attack.

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