Normally, if all goes according to plan, a human fetus develops into a healthy adult with exactly 46 chromosomes — 23 from the sperm and 23 from the egg. But just one small mistake in this process can have significant effects on the fetus, often developing into well-known disorders such as Down syndrome, which is caused by an extra copy of chromosome 21.

The developing process of a human fetus is complex, involving a multitude of processes, enzymes and other complexes that work together as one big unit. Because of its direct effect on many diseases, much research has gone into understanding this mechanism.

“We are trying to understand how these proteins work together at a molecular level and how they are regulated to do the right thing at the right time,” said senior author of the study Neil Hunter, a professor of microbiology and a member of the UC Davis Comprehensive Cancer Center research program.

During meiosis, the sexual cell division that produces sperm and eggs, matching chromosomes pair up and connect through a process known as “crossing over” — much like when two long strands of spaghetti twist together when twirled with a fork.  These crossover connections play an important role in creating sperm and eggs with exactly the right number of chromosomes.

According to Shangming Tang, a graduate student working in Hunter’s lab, each pair of chromosomes must contain at least one crossover. However, more than two crossovers per pair could damage the genome’s structure. Although scientists understand the need for chromosome crossover, research into understanding the mechanisms and enzymes through which this process occurs is only recently emerging.

“Knowing how each major pathway in meiosis is regulated will help us understand why certain syndromes occur and possibly how we can prevent or treat them,” Tang said.

In their study, Hunter and his research associates looked for enzymes that could cut DNA to form crossovers in yeast. Just like humans and other mammals form sperm and eggs, yeast form sexual gametes called spores. Through this experiment they discovered three yeast enzymes – Mlh1, Mlh3 and Sgs1 – which work to cut DNA and form crossovers.

From previous research, Hunter and his colleagues were aware of other enzymes that work together with these three. In a paper published last year, they described the discovery of enzyme Exo1, a type of enzyme called a nuclease, which is responsible for degrading DNA strands. According to Hunter, these yeast enzymes directly correlate with human enzymes; by analyzing these correlations, conclusions can be drawn.

“The human equivalents of Sgs1, Exo1, Mlh1 and Mlh3 are all tumor suppressors. What we are learning about their molecular functions is relevant for understanding what goes wrong in cancer,” Hunter said.

Hunter hopes this new discovery will help improve knowledge of certain diseases.

“Our fundamental discoveries are broadly relevant for understanding the problems that lead to various cancers, infertility, pregnancy miscarriage and [various] chromosomal diseases,” Hunter said. “We are eager to define the roles of [all] the cofactors found. So, we still have a lot to learn.”

CLAIRE MALDARELLI can be reached at science@theaggie.org.

“The goal of the C-STEM Center is to broaden participation of students typically underrepresented in computing and to develop students’ computer-aided problem-solving skills to tackle real-world STEM problems,” Cheng said. “Through various outreach activities, the C-STEM Center seeks to inspire students to pursue computing and STEM-related careers and post-secondary study.”

A new type of high-rate anaerobic digester system created by a UC Davis professor was given its first commercial application recently at a packaging plant in Sacramento. The digester allows organic solid waste to be recycled more efficiently.

Ruihong Zhang, a professor in the department of biological and agricultural engineering, created the process in the lab at UC Davis. In 2006, a research and demonstration facility was built on South Campus to test and fine-tune the process to make it ready for public and commercial use. Plans are being made to use the facility as a model for a larger facility to be built on the site of the current UC Davis landfill.

“I think it’s a very unique opportunity that we can take technology that has been developed right here on campus by Dr. Zhang and apply that to our own facilities,” said Sid England, Assistant Vice Chancellor of the UC Davis Environmental Stewardship and Sustainability program.

The planned project would convert agricultural and landscape waste created on campus, as well as leftover food scraps from the dining halls, into a fuel mixture made of 90 percent methane that could be used to fuel Unitrans buses. A mixture made of methane and carbon dioxide could also be converted into electricity for use on the campus grid, in order to be part of the West Village zero net energy project.

“Dr. Zhang’s technologies allow material that is up to 50 percent solid with no additional water added,” said Michele Wong, CEO of Clean World Partners, which has licensed the technology from the University of California and runs the new plant in Sacramento.

“Other digesters require that you have material that is much lower in solid content (10 to 20 percent), so you must add water, [which] increases the capital costs,” Wong said.

Initially foreseen as being a potentially valuable means of large-scale energy generation, anaerobic digester processing plants now are most highly valued for their ability to reduce landfill use. Reducing the amount of organic, or carbon-based, solid waste in landfills also reduces the amount of greenhouse gases released into the atmosphere, since methane, which is created when organic waste decomposes, is a highly potent greenhouse gas.

Widespread use of more inexpensive anaerobic digester processes such as Zhang’s can reduce a significant portion of the smog in California air basins. The smog is caused by volatile organic compounds (VOCs) created by the decomposition of dairy cow manure and other organic wastes.

“If we use digesters to treat manure, those VOCs won’t be formed and emitted, because the bacteria in the digesters will convert the manure into methane and carbon dioxide,” Zhang said.

Zhang’s husband, Zhongli Pan, is an adjunct professor of food engineering at UC Davis and works in the same department as Zhang. Their son, Philip, is a senior environmental engineering student at UC San Diego.

“She [Zhang] always believes that new technologies and discoveries will be the key to provide our society [with] a better living environment and make the energy supply sustainable,” Pan said.

Zhang travels frequently to China to help further advance the work in her field.

Zhang is listed as the sole inventor on two patents involving the high-rate anaerobic digester process. She is also a co-inventor of three other patents related to the process. Clean World Partners has licensed all five patents from the University of California but is currently only using two of the licenses. Zhang will receive a percentage of the royalties generated, per university policy.

BRIAN RILEY can be reached at science@theaggie.org.

I, a microbiology major, live in an apartment with a chemistry major. She often complains about the length of her lab reports — sometimes in the hard work required, occasionally in the context of how much paper and ink that it uses (as much as 10 to 15 pages for the more hellish labs).

I often don’t have much to complain about back to her. I’m in my first microbiology lab this quarter, and the lab report I completed a couple of weeks ago was required to be a grand total of three pages.

How hard do we each work? Consider this my lab report. I won’t stick with the traditional layout of a research article, as this is The California Aggie, not Science Magazine. However, I’ll introduce the majors.

Ignoring the general education requirements, a chemistry major requires 107 units total while the microbiology major requires 106 to 120 units total. The variation of the latter is mostly due to which organic chemistry class you decide to take, and, if you’re an older major, which calculus courses you took in your freshman year.

Materials and Methods

My materials and methods for answering the question I gave above, of how hard we each work, consisted just of my own observations of the requirements for each class. I can play fast and loose with these rules as, again, this is The Aggie, not Science.

Results

We spend about the same amount of time studying, but the chemistry majors spend far more time writing lab reports than I do. We biology majors have fewer and shorter lab reports, as well as labs that are nearly all discussion with few or no experiments (Physics 7, anyone?).

Discussion

Why do two science majors, both with an emphasis on research, have such differing amounts of laboratory experience? We both took the Chemistry 2 series, which is the general chemistry class. Every lab had an experiment, but mine did not require lab reports, only answering online questions that slowly walked the student through the math and what the results could mean. Biology 2 was even less demanding; though we had many worksheet questions to answer, there usually wasn’t an actual experiment or lab report.

I suppose in freshman year of college, easing the students into writing full lab reports might be a good idea, since some high schools might have been less demanding than others. However, when I compare my organic chemistry class (Chemistry 118) to the organic chemistry that the chemistry majors take (Chemistry 128), the differences become even starker. My organic chemistry class only required a lab report for a couple of the experiments; her organic chemistry class required a full lab report for all experiments.

One critique is that I’m working with a sample of only two students. This is definitely a problem with drawing definitive conclusions, although it helps that we’re both doing well in our chosen majors (there isn’t one person slacking off with grades to skew the results, for example).

At first glance, this seems like an advantage for biology majors. College students are busy enough studying as it is, especially since on the quarter system it seems like we are always in midterm season.

I know that requiring lab reports in basic chemistry and biology classes seems pointless, because the experiments that they set up are ones for which the professors already know the answer.

This grind does have a point though: practice. No one can learn to write in a certain style, especially the very precise style of lab reports, without practicing several times on an easy experiment or activity. Without this practice, many biology students will end up going into professional laboratories with two or more years less experience looking after experiments and writing their findings than chemistry or physics majors.

If the findings are something no one has ever seen before, you’re not going to have a computer program there to slowly guide you through the algebra. There won’t be a worksheet to ask leading questions. Those things can be very useful tools, especially in the beginning of a college career. But in the real world, it’s well-written lab reports that count.

AMY STEWART can be reached at science@theaggie.org.