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.
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.
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.
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...
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.
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.
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.