Tetrahymena thermophilia, a microorganism that derives its name from the Greek words for love and heat, may seem microscopic, but it is larger than life for third-year microbiology major Andrea Medina.
Medina, who participates in genetic research on single-celled organisms, received an award last month for the best undergraduate poster at the Society for Advancement of Chicanos and Native Americans in Science conference.
Medina has an emphasis on genetic engineering within the microbiology major. Her award-winning poster outlined her research on the genetics of Tetrahymena. She has been studying the organism’s DNA, and is contributing information about the organism to the scientific community. The organism can be used for many practical purposes, such as monitoring water quality.
Medina said that memories of her childhood in the Yucatan Peninsula of Mexico inspired her interest in the ocean. She originally intended to major in marine biology, but soon changed her mind.
“I took a genetics course, and it changed my whole idea,” Medina said. “We don’t have a genetics major in microbiology, so I have gone into genetic engineering.”
Her field of research often has many uninformed critics, Medina said. The phrase “genetic engineering” covers a wide area of science, some of which is very controversial.
“I think it has two sides to it,” Medina said. “You can go into one area that a lot of people are doing – the cloning, mixing and hybridizing. I just like the genetics part.”
Medina chose the genetic engineering emphasis when she became a junior after the summer in which she met one of UCSB’s most esteemed professors – molecular, cellular and developmental biology Professor Eduardo Orias. He is Medina’s mentor and has been a researching professor at UCSB since 1959. Medina applied for a stipend from the California Alliance for Minority Participation to do research last summer.
“She needed to find a mentor with about three days notice,” Orias said. “It’s the first time I accepted someone to my research group without a personal interview. I really lucked out.”
Medina’s current focus is on a single-celled organism called Tetrahymena that is commonly found in lakes and ponds around the world. The organism is unusual because it has two nuclei inside the cell. The vast majority of creatures have only one nucleus.
Orias explained that the two-nucleus system of Tetrahymena separates the genetic material that the cell uses for reproduction from the genetic material the cell uses for normal operations. This is similar to the way in which the testes or ovaries contain separate genetic material for reproduction in humans. Orias noted that this similarity makes Tetrahymena an interesting organism to study.
“There are three domains of life: the eubacteria, the archaebacteria and the eukaryotes . We are eukaryotes, and Tetrahymena are eukaryotes,” Orias said.
An eukaryotic cell is one that has a definite nucleus that contains the genetic material for the cell. The eubacteria and archaebacteria do not have a nucleus. The genetic material in those cells just floats around without being contained, Orias explained.
“Tetrahymena is being used right now to test water quality and to determine the protein – the nutritional value of food,” Medina said.
A grant given to Orias by the National Institutes of Health has helped Medina with her research.
“The National Institutes of Health just gave a grant to the lab to be able to sequence the genome, so we know where the chromosomes are and what genes they have in order for them to function in the organism,” Medina said.
A genome is the complete sequence of deoxyribonucleic acid (DNA) for an organism. DNA is composed only of four types of unique amino acids. These four kinds of acids are repeated in a pattern and linked together in a very long chain. The chain can be written in one long string of letters on paper or on a computer. Each letter represents an acid, Orias explained. Finding the genome of an organism entails recording the entire string, which is about 3.2 billion letters long for a human.
Medina’s specific research concerned finding points in the DNA that break naturally when the DNA is copied and transferred between nuclei in Tetrahymena. These points are called chromosome breakage points, Medina said.
“There are about 300 chromosome breakage points to be found. When I went to give my presentation we had found about ten; now we have about fifteen,” Medina said.
Finding the genome and the breakage points of a cell involve similar processes, Orias said. To record the DNA sequence of a cell, researchers must extract and replicate it in a process called polymerase chain reaction. This process essentially makes many copies of the existing DNA.
The next step is to cut the replicated DNA chains into many small random pieces. This is done with chemicals that break the bonds between amino acids. Four fluorescent dyes are added that bond specifically to each of the four amino acids. The dye is made to only bond to the free end of the cut pieces. After this step, each randomly cut piece of DNA has a color associated with it, which is determined by the amino acid type on the end of the chain.
The tagged pieces of DNA are put into a tray filled with gel. An electric current causes the DNA pieces to move through the gel. Larger pieces move more slowly through the gel than small pieces. This process is called electrophoresis. The method is so exact that DNA pieces differing in length by only one amino acid can be detected. A computer monitors the moving DNA pieces, and also records the color from the piece’s dye. The computer is then able to reconstruct the original sequence of DNA by putting the colors of sequentially longer pieces in order.
Her research poster outlined the results she has obtained from Tetrahymena using the above methods.
“There were about 600 people presenting from all different areas,” Medina said. “After the award ceremony, they gave out two special awards that included the best poster presentation in cell biology – the one I got.”
Other students at the conference from UCSB were Claudio Avila, Joseph Gomez and Marcos Garcia. Medina was the first UCSB student to ever win this award. Along with the award, a representative from Harvard University and MIT gave her an applications for graduate studies at both universities.
Medina said that her diligence has contributed to her success.
“I am used to working very hard. I was born and raised in Mexico, and I moved here four years ago. I didn’t know any English. I didn’t know anyone,” Medina said. “There are so many doors open; you just have to keep looking for them, and work hard to keep them open.”