HHMI's Holiday Lectures on Science
Summary: HHMI's Holiday Lectures on Science The Howard Hughes Medical Institute is a philanthropy that supports biomedical research and science education. As part of its mission to strengthen science education, the Institute presents the Holiday Lectures on Science, an annual series that brings the latest developments in a rapidly moving field of research into the classroom. These lectures are videotaped and technical, but even the lay person can learn from them. Audio files are available, but you do lose the visual aids. However, they are still useable. Previous subjects have included, dengue, RNA, and the idea of quorum sensing which is how bacteria decide when to attack, or fireflies coordinate their flashing sequence.
The lecturers Andrew Knoll and Daniel Schrag discuss topics relating to climate change as they answer questions from students in the audience. Moderated by HHMI investigator and VP of Science Education, Sean Carroll.
Students engage in a lively discussion about the film with Andrew Knoll of Harvard University; Sean Carroll, executive producer of the film; and two researchers featured in the film: Kirk Johnson, director of the National Museum of Natural History; and Tyler Lyson, postdoctoral researcher at the National Museum of Natural History.
One of the most profound questions we can ask is "Where have we come from?" Charles Darwin addressed this question in his book on human evolution, The Descent of Man, which was published in 1871. Since then, scientists have gathered fossil and genetic evidence to give shape to the human evolutionary tree. Evolutionary science, like all science, involves processes for building a body of knowledge based on reason and evidence, and requires both creativity and critical thinking.
The analysis of DNA sequences reveals the genetic heritage of modern humans. Using genetic evidence, scientists established that modern humans (Homo sapiens) originated from Africa. As groups of modern humans dispersed from Africa, they adapted to different environments around the globe. Genetic variations in human populations account for these adaptations, which continue to play a role in our lives. Examples of adaptations include what we choose to eat, what we are able to digest, and how susceptible we are to certain diseases.
Archaeology is the study of human residues using the scientific method to reconstruct human behavior. Residues are anything that results from human action, including stone tools. Tools are important in differentiating humans from other animals, and stone tools can be preserved over millions of years. By studying stone tools, scientists have learned how past human species might have lived and behaved, and how early humans differed from chimpanzees.
In 1994, scientists discovered the remarkably well-preserved fossil of "Ardi," a member of the 4.4-million-year-old species Ardipithecus ramidus. Fossils found with Ardi indicate that she lived in a woodland rather than savanna habitat. Even more surprising than her ecology is the unique combination of humanlike and chimplike anatomical features. Ardi’s remains illuminate the divergent evolutionary histories of living chimpanzees and humans.
Dr. Michael Campbell discusses how humans perceive the test of the chemical PTC. With Dr. Sarah Tishkoff, he fields questions about the evolution of taste perception, and scientific career choices.
The lecturers and science reporters Ann Gibbons and Charles Petit discuss the particular challenges that arise when communicating scientific findings to the public.
Dengue fever is a rapidly re-emerging disease that has been spreading throughout Central America and is now being detected in the U.S. It is particularly devastating in tropical countries where healthcare resources are stretched thin. Dengue virus is spread by mosquitoes, and community-based efforts to control breeding mosquitoes have been effective.
The first step in the battle against any infectious disease is to identify the infectious agent. Viruses can be identified based on their proteins or their genome. The Virochip is a DNA microarray diagnostic tool that can detect the genomes of known viruses as well as previously unknown varieties of viruses. Virochip technology is based on the basic molecular biology of DNA and RNA hybridization.
Dengue virus comes in four subtypes. Fighting off a first dengue infection increases the risk for developing a more severe form of dengue fever if they are infected a second time with a different dengue virus subtype. Dengue virus leverages the immune system to its advantage. Enhancing developing countries’ scientific and clinical infrastructure can help the international effort to counter the spread of dengue.
The Virochip has been used to identify the infectious agents of SARS and other diseases. When the Virochip alone is not enough, new DNA sequencing technologies have been used to sequence all the nucleotides in the sample. Bioinformatic tools can then identify those sequences that are of viral origin. Recent advances in sequencing technology suggest that personal genome sequencing could become routine in the not too distant future.
Mosquitoes are vectors for many viral diseases including dengue fever and West Nile. Understanding how a virus infects the mosquito is important in understanding how the disease will spread. On Grand Cayman, transgenic mosquitoes have been used in an effort to eradicate the mosquito vector. This discussion explores the ethics of genetically-modified organisms and other topics.
Natural selection has produced an astounding array of venoms for prey capture. Marine cone snails are among the most dangerous venomous creatures. Cone snail venoms are potent, deadly to fish and people, and each species makes a venomous cocktail of up to 200 different toxins. One of these toxins has been developed into a drug called Prialt–a pain killer that prevents the spinal cord from relaying pain information to the brain. With over 700 living species of cone snails, each having up to 200 unique toxins, there are potentially more than 140,000 novel molecules with drug potential.
Bacteria live in and on us in complex communities that outnumber the cells and genes of our own tissues. These bacteria possess a communication mechanism that allows them to coordinate their activities. This mechanism, called quorum sensing, was first described in bacteria living symbiotically in a squid. The bacteria produce bioluminescence which simulates moonlight and camouflages the squid. The key to quorum sensing is a molecular signal released by the bacteria that is monitored by receptors, which in turn modulate gene expression. Bioluminescence genes are only turned on when the population density–and therefore the signal concentration–is high.