Question 1

Why is Saccharomyces cerevisiae considered a model organism for research?

Accepted Answer

S. cerevisiae is an ideal model organism because its genome has been fully sequenced and is publicly available, its genetics are easily manipulated, and it grows quickly in the lab with minimal equipment. Additionally, many yeast proteins share similar sequences with proteins in higher eukaryotes, allowing researchers to understand fundamental cellular processes like cell division and cell death that apply across species.

Question 2

How does yeast cell division differ from typical eukaryotic cell division?

Accepted Answer

S. cerevisiae divides through budding, an asexual process where a newly synthesized bud forms from the mother cell and grows until cytokinesis. Unlike typical eukaryotic mitosis, which produces two equal-sized daughter cells, budding results in unequal cell sizes. Yeast cells divide approximately every 90 minutes, making them efficient for laboratory study.

Question 3

What are shuttle vectors and how are they used in yeast research?

Accepted Answer

Shuttle vectors are plasmids that can propagate in two different species, such as E. coli and S. cerevisiae. This dual capability allows molecular cloning to be performed in E. coli first, then introduced into yeast. Yeast integrative plasmids, a type of shuttle vector, enable incorporation of foreign DNA into the yeast genome through homologous recombination, allowing genes to be knocked out or swapped permanently.

Question 4

What historical discoveries about cell regulation came from yeast research?

Accepted Answer

In the 20th century, Hartwell and Nurse discovered proteins regulating the cell cycle in yeast, identifying cyclin and cyclin-dependent kinase as key regulators of cell division. These highly conserved proteins are critical for understanding dysregulation of the cell cycle in multicellular organisms, which can lead to cancer. Later, Blackburn, Greider, and Szostak discovered telomerases and their role in maintaining chromosome ends.

Question 5

How does yeast fermentation produce alcohol?

Accepted Answer

In the absence of oxygen, S. cerevisiae switches to fermentation, a metabolic process that allows yeast to break down sugars. During fermentation, pyruvate produced by glycolysis is reduced to acetaldehyde, which is then converted to ethanol through the reduction of NADH to NAD+. This process, identified by Luis Pasteur in 1856, is the basis for wine-making and bread-baking.

Question 6

What is autophagy and why is it important for studying disease?

Accepted Answer

Autophagy is a cellular recycling process where expendable organelles are engulfed by an autophagosome, which then fuses with a lysosome to break down proteins into amino acids for new protein synthesis. Discovered by Ohsumi in 1992, autophagy protects against invading pathogens and tumor growth. Yeast research on mitophagy, the removal of damaged mitochondria, has implications for understanding Alzheimer's and Parkinson's diseases.

Question 7

What are the main applications of yeast in modern biomedical research?

Accepted Answer

S. cerevisiae is used to express and purify large amounts of proteins, such as the cystic fibrosis transmembrane conductance regulatory protein, for structural studies. Yeast also serves as a model system for genetic studies of human DNA repair proteins that detect and fix damaged DNA. Additionally, yeast enables researchers to study cellular processes related to aging, disease mechanisms, and protein function through fluorescence microscopy and Western blot analysis.

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