Aging involves an intrinsic and progressive decline in function that eventually will affect us all. While everyone is familiar with aging, many basic questions about aging are mysterious. Why are older people more likely to experience diseases like cancer, stroke, and neurodegenerative disorders? What changes happen at the molecular and cellular levels to cause the changes that we associate with old age? Is aging itself a disease, and can we successfully intervene in the aging process?This course is one of many Advanced Undergraduate Seminars offered by the Biology Department at MIT. These seminars are tailored for students with an interest in using primary research literature to discuss and learn about current biological research in a highly interactive setting. Many instructors of the Advanced Undergraduate Seminars are postdoctoral scientists with a strong interest in teaching.

Two lessons and their associated activities explore cellular respiration and population growth in yeasts. Yeast cells are readily obtained and behave predictably, so they are very appropriate to use in middle school classrooms. In the first lesson, students are introduced to yeast respiration through its role in the production of bread and alcoholic beverages. A discussion of the effects of alcohol on the human body is used both as an attention-getting device, and as a means to convey important information at an impressionable age. In the associated activity, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arise from this activity, in the second lesson students work in small groups as they design and execute their own experiments to determine how environmental factors affect yeast population growth.

The need to identify sustainable forms of energy as an alternative to our dependence on depleting worldwide oil reserves is one of the grand challenges of our time. The energy from the sun converted into plant biomass is the most promising renewable resource available to humanity. This seminar will examine each of the critical steps along the pathway towards the conversion of plant biomass into ethanol. This course is one of many Advanced Undergraduate Seminars offered by the Biology Department at MIT. These seminars are tailored for students with an interest in using primary research literature to discuss and learn about current biological research in a highly interactive setting. Many instructors of the Advanced Undergraduate Seminars are postdoctoral scientists with a strong interest in teaching.

Students set up and run the experiments they designed in the lesson Population Growth in Yeasts, using simple yeast-molasses cultures in test tubes. Population growth is indicated by the amount of respiration occurring in the cultures, which in turn is indicated by the growth of carbon dioxide bubbles trapped within the culture tubes. Using this method, students can test for a variety of environmental influences, such as temperature, food supply, and pH.

" This seminar is designed to be an experimental and hands-on approach to applied chemistry (as seen in cooking). Cooking may be the oldest and most widespread application of chemistry and recipes may be the oldest practical result of chemical research. We shall do some cooking experiments to illustrate some chemical principles, including extraction, denaturation, and phase changes."

Genomic and plasmid-encoded RAS2 genes from Baker's and brewing yeast strains will be analyzed using a shortened Southern blot procedure employing chemiluminescence. Unique parts of this procedure are the gravity-driven "upside down" transfer and a rotisserie-like hybridization oven, which greatly facilitate shortening the transfer time to 45 minutes and the hybridization step to 60 minutes. Chemiluminescence obviates problems associated with radioisotopes without sacrificing sensitivity: the plasmid-borne RAS gene can be visualized within 15 seconds and the single-copy yeast genomic RAS2 gene, within a minute. Topics for discussion related to this laboratory can include the concepts of RFLPs, evolutionary conservation of DNA sequences and the genetic basis of cancer.

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, in this lesson students work in small groups to design experiments that will determine how environmental factors affect yeast population growth.

In this activity, students act as environmental engineers involved with the clean up of a toxic spill. Using bioremediation as the process, students select which bacteria they will use to eat up the pollutant spilled. Students learn how engineers use bioremediation to make organism degrade harmful chemicals. Engineers must make sure bacteria have everything they need to live and degrade contaminants for bioremediation to happen. Students learn about the needs of living things by setting up an experiment with yeast. The scientific method is reinforced as students must design the experiment themselves making sure they include a control and complete parts of a formal lab report.

Students are presented with information that will allow them to recognize that yeasts are unicellular organisms that are useful to humans. In fact, their usefulness is derived from the contrast between the way yeast cells and human cells respire. Specifically, while animal cells derive energy from the combination of oxygen and glucose and produce water and carbon dioxide as by-products, yeasts respire without oxygen. Instead, yeasts break glucose down and produce alcohol and carbon dioxide as their by-products. The lesson is also intended to provoke questions from students about the effects of alcohol on the human body, to which the teacher can provide objective answers.

This exercise examines when adaptive mutations arise in a population. Students prepare cultures of baker's yeast on normal agar media and then transfer the exact spatial pattern of these colonies to agar plates containing copper using the replica-plating technique. They compare the pattern of mutant colonies on the two replicate plates to test when copper-tolerant mutants arose. If the colony positions match then the mutants pre-existed in the original population (spontaneous mutation). If colonies do not match then this supports a hypothesis that mutants were induced by exposure to the copper. Students learn skills such as preparing agar plates, the sterile technique, replica-plating, and the use of pipets and dilutions.