The Y chromosome has been likened to a hall of mirrors because its sequence contains many sections that appear to be palindromes. These palindromes provide a clue to some interesting events that may have occurred during the course of the chromosome's evolution.
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.
A sample is put on a Virochip microarray, and results are compared to databases of all known viral sequences.
Delivering a single virus to a cell allows the virus to infect the cell, replicate, and give rise to many progeny viruses. These viruses can then infect many neighboring cells.
The geometric structures of viruses are beautiful and can be used, along with genomic information, to identify them.
This animation shows how a growing tumor can recruit nearby blood vessels in order to gain a supply of blood.
This animation illustrates how a small molecule binds to a protein. As a result of the binding, the protein alters its shape and becomes inactivated.
This animation demonstrates how cancerous cells could be destroyed using a modified virus.
A visual representation of the U.S. AIDS epidemic from 1981 to 1997. Each dot represents 30 cases.
Slippage during DNA replication can lead to expanding sections of repeating nucleotides. Watch this animation to see how this problem occurs.
View the animation to see how one type of immune cell—the helper T cell—interprets a message presented at the surface of the cell membrane. The message is an antigen, a protein fragment taken from an invading microbe. A series of events unfolds that results in the production of many clones of...
A quarry site in Nevada carries the evolutionary history of a population of stickleback fish that resided there when it was a freshwater lake.
This animation shows a rotating 3-D image of a stickleback skeleton. The pelvic region, including the pelvic spines, is highlighted in red. Armored plating covers the flanks of the fish. The three prominent dorsal spines give the fish its name.
A molecular menagerie of small molecules is displayed, with two particular molecules singled out for attention: rapamycin and furrowstatin, which are discussed in the remainder of Dr. Schreiber's lectures on chemical genetics.
Microarray technology is useful for screening many small molecules at once. Automated devices have made it possible for thousands of different small molecules to be printed as an array of spots on a glass slide. A single type of protein which has been tagged with a fluorescent marker can then...
Varying concentrations of a signaling molecule activate different transcription factors and determine cell fate.
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...
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...
Illustrates how studying one family's pedigree can reveal an entire history of passing on a genetic disorder such as SCA1.
In this animation, you can see how one S. typhimurium invades an epithelial cell of the intestinal tract, survives the intracellular defense mechanisms of the host cell, and multiplies.
The growth cone of a neuron avoids repellant molecules and navigates to innervate the appropriate muscle.
When two different strains of influenza infect a single cell, their genetic material can mix freely, resulting in a new third strain of influenza.
Rapamycin is a small molecule originally isolated from nature. It has antibiotic and immunosuppressive properties. It also allows two proteins which do not normally interact to bind together in the cell, which causes problems in the nutrient-sensing pathway.
Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex?
This animation illustrates how mistakes made during DNA replication are repaired.
Quorum sensing regulates gene expression by a protein phosphorylation cascade that controls transcription.
Prialt does not block the mammalian motor synapse, but blocks the pain pathway in the spinal cord.
Prialt, a drug derived from cone snail venom, paralyzes fish by blocking calcium channels at a motor synapse.
The PPAR-gamma receptor activates certain genes in a fat cell, resulting in the storage of fat and changes in hormone levels.
The PPAR-delta receptor activates certain genes in a muscle cell, resulting in the burning of fat.
The rock pocket mouse is found in two color variants, or morphs: light and dark. In different environments, their visibility to predators such as owls varies. The dark morph is more vulnerable on light sandy desert, and the light morph on dark lava rock.
This simulation shows the spread of a favorable mutation through a population of pocket mice. Even a small selective advantage can lead to a rapid evolution of the population.
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...
PCR is a standard laboratory technique that allows amplification of specific segments of DNA based on complementarity.
In two related Drosophila species, a so-called paintbrush gene is activated to "paint" the pigment on the body. In one species, an extra switch activates the gene, resulting in spotted wings.
A 3D animation showing the molecule p53 binds to DNA and initiates the transcription of mRNA.
Urodele amphibians—newts and salamanders—are able to regenerate fully functional limbs in response to amputation. Cells in and near the limb stump dedifferentiate to form a mass of stemlike cells that can produce all the specialized tissues of the limb, such as muscle, nerves, and blood vessels...
Neurons in the cortical area 5 are active when a cat is straddling an obstacle.
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.
Multiple cone snail toxins attack different molecules of the nervous system and cause paralysis.
After a chemical biologist has made many novel small molecules by diversity-oriented synthesis, the next step is to find those that are useful. Molecules need to be "screened." Conceptually, screening is like using proteins as a custom filter to catch potentially useful small molecules.
Electrical and chemical signals are used by neurons to communicate with one another at contact points called synapses.
This animation shows how the protein MECP2, in conjuction with another protein complex, can act as an "on-off' switch for gene expression.
This animation shows the molecular interactions involved in the negative feedback loop responsible for circadian rhythms in mammals.
This animation series shows four experiments that compare the activity patterns of a wild-type fly keeping a normal schedule with those of a mutant fly apparently following a 19-hour internal clock.
A cancer tumor forms in a bed of healthy cells. The animation goes on to show how the tumor recruits blood vessels and how metastasis occurs.
Long-term memory requires the activation of CREB, turning on specific genes that support new synaptic growth.
Short-term memory relies on serotonin activating a protein kinase to modify existing synaptic strength.
Comparison of the change in BMI for a given height and varying weights.
One technique for discovering small molecules of biological relevance is to expose cultured cells to a variety of small molecules and look for changes in the cells' appearance, behavior or other measurable qualities.