2644 - CSUN ScholarWorks - California State University, Northridge

journal of Student Research Abstracts · 19
cereus only grew on live E. coli or on dead bacteria because it spread outside of the original streak and into
another unstreaked area in both samples. Therefore, I concluded that interspecies conjugation did indeed occur.
2677
EFFECT OF YEAST ON THE ROTTING OF APPLES.
Wayne To and Steven DeGusta, (teacher). John F. Kennedy High School, 6715 Gloria Drive, Sacramento,
CA 95831.
Rotting is the leading cause of fruit industry losses. A possible way help fight rotting is the addition of a
naturally-occurring organism such as yeast, which can thrive inside fruit and prevent any pathogens from
invading and destroying the fruit. To test the effects of yeast on the rotting of apples, a cube was cut out of each
apple (wound) and purposely infected with fungi to induce rotting. One experiment involved the addition of
baker's yeast (Saccharomyres cerevisae) to ten test apples. Red yeast (Rhodotorula rubra), a relative to
Rhodotorula glutinis, a successful biocontrol for pears, was also added to eight apples and were considered the
other test group. Both controls groups were left out to rot without the addition of the yeast.
The results show that those apples with red yeast applied had only a small effect on the decay of the apple
when compared with their control counterparts (t > 0.1). The baker's yeast, on the other hand, had no effect on
the rotting of the apples. The red yeast did show that it could slow down the rotting process. A possible reason
for the yeast having little effect is that it was outcompeted by the fungi since the fungi came straight from
growth on previously rotted apples. Also, the in another test, it was shown that on five plates of potato dextrose
agar, fungi from rotted apples grows in a way that will take up more space than red yeast. This means that the
fungi will eventually outcompete the yeast for available living space. In order for an effective biocontrol to be
found, a strain of yeast that can grow well on apples is needed to test its effectiveness against rotting.
2278
SURVIVAL OF THE FITTEST.
Ronald L. Lew and Steve DeGusta (teacher). John F. Kennedy High School, 6715 Gloria Drive,
Sacramento, CA 95831.
The purpose of this experiment was to test if deformed wings affect the selection of a mate between flies. To
test this, the male homozygous wild flies, male homozygous vestigial (genetically wingless) flies, and the female
heterozygous wild flies were placed into one culture. The offspring would determine which types of flies were
chosen as a mate. Another combination that I used was male homozygous wild flies, male homozygous vestigial
flies, and female homozygous vestigial flies were placed into a culture. In order for my experiment to work,
the cultures must be prepared properly. I mixed the Drosophila medium with water and placed it into a culture. I
used approximately 5 ml of water and 5 ml of medium. This medium acts like a spoiled fruit in which the flies
lay their eggs, which in tum, turns into adult flies. The flies had to be etherized before transferring them into a
culture. If not etherized, the wild flies would simply fly away. There were a total of 22 cultures. 11 cultures had
2 male homozygous wild flies, 2 male homozygous vestigial flies, and 2 female heterozygous wild flies in it. The
remaining 11 had 2 male homozygous wild flies, 2 male homozygous vestigial flies, and 2 female homozygous
vestigial flies in it. There were 10 cultures that the offspring were only wild flies. 3 of the 10 had 2 male homozygous
wild flies, 2 male homozygous vestigial flies, and 2 female heterozygous wild flies initially. The remaining
7 had 2 male homozygous wild flies, 2 male homozygous vestigial flies, and 2 female homozygous vestigial flies
initially. The other 11 cultures had a mixture of wild and vestigial flies. I look at the phenotype of the flies when
determining whether the flies are wild or vestigial. I cannot conclude from this experiment that the wild flies have
an advantage over the vestigial flies when the female chooses a mate because only half of the vials have only wild
flies for offspring. If this lab were to be done over again, I would have 1 female fly in each culture. This would
make it easier when determining which type of fly mated with the female flies. If a male homozygous vestigial
fly mate with a female fly and a male homozygous wild fly mate with a female fly in the same culture, then it
would be difficult to determine which flies were the parent flies. (p