This animation shows how the random deactivation of one of the X chromosomes in a pair can lead to a mozaicism in the expression genes.
This animation shows how a growing tumor can recruit nearby blood vessels in order to gain a supply of blood.
In mammals, the controlling clock component that generates a 24-hour rhythm is the suprachiasmatic nucleus (SCN), located in a part of the brain called the hypothalamus. The SCN produces a signal that can keep the rest of the body on an approximately 24-hour schedule. This animation illustrates...
A 3D animation showing how proteins in the cell are tagged for disposal and degraded by the proteasome.
Myosin II is one of the molecules involved in furrow formation in dividing cells. This animation shows how the molecule operates, and how furrowstatin blocks the mechanism and halts division of a cell.
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.
Infection begins when the dengue virus uses receptors on an immune cell's surface to gain entry and release its genome.
This animation describes two different ways by which chemicals migrate through membranes: passive diffusion and active transport.
DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.
Watch this animation to see the molecular tricks that an infectious strain of Escherichia coli uses to infect your gut.
A demonstration by Dr. Meyer showing how a balance of molecular elements trigger genetic pathways that determine the sex of a C. elegans worm.
Time-lapse microscopy showing cell division from 1 to 2 to 4 cell stages in C. elegans with fluorescent chromosomes.
Video of the fertilization of the C. elegans oocyte, the fusion of the egg and sperm nuclei, and the egg laying.
Video closeup of the C. elegans sperm that moves like an amoeba.
Video microscopy of a cytotoxic T lymphocyte in action.
Why has it been so hard to develop a vaccine against HIV? How are new medicines revolutionizing AIDS treatment? Can AIDS be cured?
In four presentations, Donald E. Ganem, MD, and B. Brett Finlay, PhD, discuss the latest advances in understanding how pathogens invade the body and how this knowledge is leading to the development of new therapies. They also explain how new infectious diseases are recognized and how epidemics...
Dr. Brett Finlay explains why bacterial diseases continue to be a major health problem worldwide, causing a third of the world's deaths every year.
Dr. Finlay showcases three types of bacteria to illustrate how molecular biology is allowing researchers to probe the molecular workings of bacterial infections.
Venomous carniverous cone snails are a rich source of molecules for scientific research and potential drug development.
Bacteria are capable of communicating and coordinating their activities with a molecular signaling system called quorum sensing.
The quorum sensing system is a target for a new class of drugs that interfere with virulence without killing bacteria.
In this 13-minute Q&A session, Dr. Bonnie Bassler answers questions on quorum sensing and other topics related to bacteria.
How a nerve cell gets its identity, sends axons, and makes connections with other cells.
The cellular and molecular nature of learning and memory, investigated in simpler sea slugs and more-complex mice.
As part of the 2003 Holiday Lectures on Science, Dr. Bert Vogelstein and Dr. Huda Y. Zoghbi discuss how their patients have led to a deeper understanding of the genetic and molecular bases of neurological disorders and cancer. Thanks to these patients, researchers can now apply the knowledge...
Although there are numerous kinds of cancer, all stem from alterations that allow cell division to outstrip cell demise.
The identification of hundreds of genes involved in the formation and spread of cancer is leading to promising new methods for diagnosis, prevention, and treatment.
Mutations in key genes can lay waste to the nervous system. By studying large families predisposed to developing these genetic disorders, scientists can identify the responsible altered gene.
Girls with Rett syndrome develop normally for about 18 months and then begin to regress. With the help of affected girls and their families, Dr. Zoghbi and her collaborators searched for the gene responsible for this neurological disorder.
In four talks, A. James Hudspeth, MD, PhD, and Jeremy H. Nathans, MD, PhD, discuss how sensory information is encoded and transmitted to the brain. They describe the detailed workings of two senses of great importance to humans—vision and hearing.
Dr. Hudspeth will begin by discussing how simple organisms—such as bacteria—have the capacity to detect and react to a stimulus.
Dr. Nathans will discuss how the visual process involves the detection of light by photo-receptors in the retina.
Dr. Hudspeth will explain the basis for the ear’s remarkable ability to detect sound through the hair cell, the sensory receptor found in the inner ear.
Dr. Nathans will complete the lecture series by clarifying what is known about the brain’s ability to process and integrate various elements of the visual system, such as color, motion, and depth.
An overview of embryonic development, the progressive differentiation of cells, and properties of embryonic stem cells.
The role of stem cells in regeneration, and ongoing research to improve mammalian regeneration potency.
In cloning, a cell's genetic machinery is reprogrammed. Can we similarly coax stem cells to become specific cell types?
Finding factors to reverse age-related loss of cell maintenance, and some examples of stem cell therapies.
Dr. Evans reviews how PPARs regulate body weight by controlling whether fat is burned or stored.
A Q&A session on obesity and related issues, with the lecturers and students attending the Holiday Lectures on Science.
Four talks focus on sex determination—the molecular and genetic mechanisms that determine whether an organism will be male, female or a hermaphrodite.
Is it a boy or a girl? Dr. David Page looks at how we define male and female and summarizes the development of human sex characteristics.
Dr. Barbara Meyer explains the value of studying model organisms and introduces the nematode C. elegans.
Having too many chromosomes can lead to too much gene expression. Dr. Meyer explains how the gene that controls dosage compensation in C. elegans works.
Dr. Page explains how successive inversions and deletions of the Y chromosome during mammalian evolution have reduced it to its present form—small and sparsely populated with genes.
Four lectures highlight the research of two scientists who have made groundbreaking discoveries elucidating the molecular basis of circadian clocks—the internal timekeepers that govern fluctuations in behavior and physiology on a 24-hour cycle.
Although tiny in size, the fruit fly has had a major impact on our understanding of circadian rhythms.
Dr. Rosbash discloses how scientists have persuaded Mother Nature to reveal the inner workings of the fruit fly's biological clock.
Dr. Takahashi describes the powerful strategies that he and others have harnessed for understanding biological clocks in mammals.
A hands-on activity in which students construct models of sickle-cell hemoglobin fibers inside red blood cells to illustrate how changes in the structure of a protein can affect cell shape. Students are then asked to relate these changes to disease symptoms.
The poster from the 2008 Holiday Lectures on Science, Making Your Mind: Molecules, Motion, and Memory. It illustrates the structure and function of a neuron, including how it transmits electrical and chemical signals.
(This poster is designed to printed at a maximum size of 29.5...
The poster from the 2007 Holiday Lectures on Science, AIDS: Evolution of an Epidemic. It shows each stage of the HIV life cycle and highlights points in the cycle that have been targeted by anti-retroviral drugs.
A wide overview of the immune system, presented by HHMI investigators John W. Kappler, PhD, and Philippa Marrack, PhD
The human body has at least a trillion ways of recognizing that something foreign has invaded.
The immune system recognizes invaders in a complex way.
Normally the trillions of lymphocytes in the human body do not attack their host.
Some organisms have evolved ways of evading or subverting the body's defenses.
In the 2013 Holiday Lectures on Science, leading medical researchers explain how advances in genomics are revolutionizing their work, leading to a better understanding of disease and to improved treatments.
A brochure from the 2013 Holiday Lectures on Science.
Sponges feed themselves through chambers of specialized cells.
The young starlet sea anemone forms tentacles by cell division, migration, and shape changes.
Recent advances in DNA sequencing technology have led to a better understanding of the many genes that play a role in brain development.
Understanding that cancer is caused by mutations in genes that regulate cell proliferation has led to the development of targeted drug therapies.
Genetic data from a large number of tumor types reveal commonly mutated genes and uncover connections between different types of cancer.
The Cape Cliff lizard sports a bony body armor.
Disrupting the normal processes of differentiation and maturation of the intestinal epithelial cells can lead to cancer.
Chromosomes change form as a cell divides to ensure that each daughter cell gets a full, intact copy of the genome.
The human immunodeficiency virus (HIV) is discovered “hiding” between the cells of the gut.
The arrangement of cells in the retina reveals how it detects, processes, and relays visual information to the brain.
A unique group of cells in the eye’s retina specifically detects the upward motion of objects, such as a ball thrown in the air or…fireworks.
What medical secrets do venomous snails hold? How can listening in on bacterial conversations help develop new antibiotics? In four presentations, Dr. Bonnie L. Bassler and Dr. Baldomero M. Olivera reveal how a deeper understanding of nature and biodiversity informs their research into new...
A weekly image selected from the striking imagery produced every day by scientists around the world.
The small molecule 'furrowstatin' exemplifies the power of using small molecules to investigate life's processes. When applied to dividing cells, the furrowstatin halts cell division.
The poster from the 2006 Holiday Lectures on Science, Potent Biology: Stem Cells, Cloning, and Regeneration, illustrates the role of stem cells during human embryonic development.
Zebrafish blood is generated from stem cells located in the tail region of fish embryos and later from stem cells located in the kidney of the adult fish.
In the 2004 Holiday Lectures on Science, HHMI investigators Ronald M. Evans and Jeffrey M. Friedman discuss how the body regulates weight by carefully controlling the storage and burning of fat—and how a better understanding of these complex metabolic systems could lead researchers to...
Dr. Friedman introduces the genes and circuits that control appetite, including the key role of leptin.
Reef-building corals depend on brown-colored symbiotic algae for survival.
Two views of a late pupa of an unidentified midge species (family Chironomidae).