Fruit Flies Experiment
Results
1. Female Wild Type (+) & Male Wild Type (+) = 100% Wild Types
From the result extracted from above, it can be seen that the outcome is “obvious” in terms of
probabilities that it will be 100% wild types since the two “parent” flies are homozygous dominant.
Therefore, we can see that there is a complete dominance since the only result we expect to see in
terms of probability is offspring that are wild types.
2. Female Wild Type (+) & Male Vestigial (vg) =
100% Wild Type (+) [F1 Generation]
66% Wild Types & 33% Vestigial (3:1) [F2 Generation]
From the result shown above, there are two things that can be seen clearly. First of all, we can see
the fact that the wild type genotype is more dominant than the vestigial genotype. This is because,
we can see that the F1 Generation have flies that have phenotypes of wild type flies. But looking at
the F2 Generation, it is also visible that these flies aren’t homozygous dominant but are
heterozygous dominant since the F2 Generation does not have 100% chance of having a wild type
offspring and instead there is also a possibility of having a vestigial offspring. Second of all, the
type of dominance can also be seen by looking at the F1 and F2 generations since the F2 generation
insists that there isn’t a complete dominance since there is a chance of having an offspring with a
recessive trait. Therefore, the type of dominance that can be seen in this mating is an incomplete
dominance of the wild type over the vestigial with a ratio of 3:1.
3. Female Wild Type (+) & Male Apterous (ap) =
100% Wild Type (+) [F1 Generation]
66% Wild Types & 33% Apterous (3:1) [F2 Generation]
Just like the above description, it is again clear that the wild type genotype is clearly dominant over
the apterous genotype since the ratio clearly shows that (wild type:apterous = 3:1). From this, we
can see again that the F1 Generation of flies will have a heterozygous dominant genotype and
therefore will be carriers of the apterous/recessive genotype. And again, the type of dominance of
the wild types over the apterous is an incomplete dominance.
4. Female Vestigial (vg) & Male Wild Type (+) =
100% Wild Type (+) [F1 Generation]
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Fruit Flies Experiment
66% Wild Types & 33% Vestigial (3:1) [F2 Generation]
From this result, we can make the same conclusion as the conclusion we made in mating 2. Since
this also clearly shows the fact that wild type is clearly a dominant trait compared to the vestigial
and also the fact that the F1 generation of flies will just be carriers of recessive traits but will have
the phenotype of the wild type since the F2 generation prove to us that the F1 generation is not
“pure homozygous dominant”. And again, the type of dominance here is the incomplete dominance
of the wild type over the vestigial with the probability ratio of 3:1.
5. Female Vestigial (vg) & Male Vestigial (vg) = 100% Vestigial (vg)
From this result, we can see that when we mate two vestigial fruit flies, the outcome will probably
be 100% vestigial. This tells us that the offspring will be homozygous as long as there are no
“outside forces” such as mutations to disrupt the hereditary. And therefore, the type of dominance
here is a complete dominance of the vestigial trait since there is no room for a probability of another
trait to rise.
6. Female Vestigial (vg) & Male Apterous (ap) =
100% Wild Type [F1 Generation]
50% Wild Types & 25% Vestigial & 25% Apterous (2:1:1) [F2 Generation]
This set of result is really interesting. There are two things that can be seen from this result. 1. The
important fact that the trait of fruit flies (wings) is polygenic. In other words, the wings of fruit flies
are controlled not only by one specific genotype but more than one genotype. Therefore, the
mating between vestigial and apterous (dihybrid cross) gave us the result of actually having a F1
generation of 100% wild type but a 50% wild type, 25% vestigial, and 25% apterous. Another thing
that we could see is the fact that there was a co-dominance between the vestigial and apterous
genotype which lead to the dihybrid cross allowing a wild type to rise in the F1 and F2 generations.
7. Female Apterous (ap) & Male Wild Type (+) =
100% Wild Type [F1 Generation]
66% Wild Types & 33% Apterous (3:1) [F2 Generation]
This result tells us that the wild type genotype is dominant compared to the apterous genotype.
This result also tells us the fact that the offspring from the F1 generation will have a heterozygous
dominant since the F2 generation doesn’t have 100% wild types but instead have a possibility of
having apterous too, therefore, this result also tells us that the F1 generation wild types are
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Fruit Flies Experiment
heterozygous dominant. The last thing this result tells us is the fact that there is an incomplete
dominance of the wild type over the apterous since there is a possibility of having an apterous
offspring but there is a higher chance of having an offspring which is a wild type.
8. Female Apterous (ap) & Male Vestigial (vg) =
100% Wild Type [F1 Generation]
50% Wild Types & 25% Apterous & 25% Vestigial (2:1:1) [F2 Generation]
Looking at this set of result, we can make a similar conclusion as the mating that happened in 6.
The thing we can see again is the fact that the wings of fruit flies are not determined only by one
gene but can be determined by many genes (polygenic). And this is why when we mated the
apterous and vestigial fruit flies, we still have room to get wild types. Therefore, because when we
mated the apterous and vestigial, we were doing a dihybrid cross where two genes were “put into
action”, we were able to get an incomplete dominance of the wild types over the apterous and
vestigial with a ratio of 2:1:1.
9. Female Apterous (ap) & Male Apterous (ap) = 100% Apterous
From this result, we can see that the offspring from this mating will most likely be a homozygous
fruit fly since when we mate apterous with apterous, it is impossible to have another type of gene
interfering logically unless there are outside forces such as mutations that could affect the mating.
Therefore, we can see that the type of dominance here is a complete dominance of the apterous
genotype since again, there is no possibility to get another type of genotype if we mate 100%
apterous fruit flies with each other.
Conclusion
From the above lab results, we can clearly see a lot of things. First of all, we can clearly see the fact
that being a wild type means that the fly is either heterozygous or homozygous dominant therefore,
being a wild type is a dominant trait. Another thing that we can see is, any fruit fly that is either
Vestigial or an Apterous is always going to be homozygous recessive and this is clearly shown when
we started to cross Vestigial with wild types and Apterous with wild types too. This is because, the
result of the F1 generation was of course 100% wild type since the wild type is a dominant trait so
there was an incomplete dominance. However, the interesting part was the F2 generation since the
F2 generation indicated that there was a 3:1 ratio between the wild types vs. vestigial and the wild
types vs. apterous. We can also see the dominance between the two types of genotypes by looking
at these results. First of all, when we mated the female vestigial fly with the male wild type, we
could clearly see that the wild types had an incomplete dominance over the vestigial and it wasn’t
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Fruit Flies Experiment
a complete dominance nor a co-dominance since 1. The ratio told us that there was a possibility of
having a vestigial offspring and 2. There was clearly a higher chance of having a wild type offspring
than a vestigial offspring. However, when we mated the female vestigial with the male vestigial, (two
identical genotypes), we could see that there was a complete dominance since the outcome would
be a phenotype of being vestigial 100%. The most interesting part came when there was a mating
between the female apterous flies and the male vestigial types since this clearly showed a codominance. A co-dominance is when two genotypes are equally dominant which creates a very
interesting ratio. An example is when there is a mating between two opposite sexed humans that
have a blood type A and blood type B because, when they have a mating, there is a 25% chance
of having an AB offspring, B offspring, an offspring, and an O offspring. This is because, there is
something sort of a dihybrid cross and when there is a dihybrid cross forming, it is possible that
the specific “new genotype” can affect the fruit flies to become wild types. Therefore, we can see
that the ratio that is created when we mated the two vestigial and apterous fruit flies resulted
because of the co-dominance that existed between the two genotypes which brings us to a
conclusion that wings of fruit flies are actually polygenic since two genotypes do affect the outcome
of the wings of fruit flies. Another really important thing that we need to realize is the fact that this
trait (wings) of fruit flies are not sex-linked since when we had a male apterous mating with a female
wild type and the male wild type mating with a female apterous, the possibility was identical.
Therefore, from these sets of results, one thing we’re sure is that the wings of fruit flies are not sexlinked traits.
Analysis
There were some very simple mistakes that could’ve been made in this experiment and one of them
is the fact that the results from this experiment was all calculated in probabilities, therefore, the
“exact” possibility of the fruit flies that could’ve resulted from the mating had to be analyzed and
converted into a ratio therefore, the approximation that was made from the experiment could’ve
lead to a result that could possibly be wrong. Another mistake that could’ve been made was again,
because of the fact that we used probabilities in this experiment. The reason why using probabilities
can result to an inaccurate result is because, there are much more natural factors that could affect
the genotype/phenotype of the fruit flies. Therefore, the fact that we over-generalized the fruit flies’
environment of being a “perfect” environment could’ve made us have results that could be flawed.
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