Construct a grid analogous to Figure 12.16 found in the textbook, in which you cross
two TtIi individuals.
F1 generation: Ttli
T1
Ti
tl
ti
Tl
TTll
TTli
Ttll
Ttli
Ti
TTli
TTii
Ttli
Ttii
tl
Ttll
Ttli
ttll
ttli
ti
Ttli
Ttii
ttli
ttii
F2 generation
Tall and inflated: 9
Tall and constricted: 3
Dwarf and inflated: 3
Dwarf and constricted: 1
The phenotype ratio 9:3 :3 : 1
You cross the dwarf and tall plants and then self-cross the offspring. For best results.
this is repeated with hundreds or even thousands of pea plants. What special
precautions should be taken in the crosses and in growing the plants?
The purpose of this experiment is to be as precise as possible and special precautions need to
be taken against unwanted pollination. For this experiment, the plants can be pollinated via
wind, animals, or insects (Blamire, 1997). Measures need to be taken to prevent any
accidental or unwanted pollination. Also, it would be best to do what Mendel did and
pollinate each plant by hand so that you can ensure which plants get pollinated (Avissar et al.,
2013). To prevent self-pollination, the anthers of the plants can be removed before maturity
(Avissar et al., 2013).
You observe the following plant phenotypes in the F2 generation: 2706 tall/inflated, 930
tall/constricted, 888 dwarf/inflated, and 300 dwarf/constricted. Reduce these findings to
a ratio and determine if they are consistent with Mendelian laws.
The hypothesized ratio is 9:3:3:1. The given results will also have to be reduced to a ratio. We
can put it into a ratio as follows 2706:930:888:300. At first glance, the numbers are not
exactly 9:3:3:1 but they are definitely very close. We cannot simplify this entire ratio to one
clean and round number, but we can see the middle numbers are roughly 3 times that of the
last number and the first number is roughly 9 times that of the 4th number. We can say that the
results are consistent with the Mendelian laws.
Were the results close to the expected 9:3:3:1 phenotypic ratio? Do the results support
the prediction? What might be observed if far fewer plants were used, given that alleles
segregate randomly into gametes? Try to imagine growing that many pea plants, and
consider the potential for experimental error. For instance, what would happen if it was
extremely windy one day?
The results were not an exact 9:3:3:1 ratio but they were extremely close and therefore the
results are consistent with the hypothesis made. if there were fewer plants, there is a very real
chance that the results would be skewed and would not line up with the ratio made in the
hypothesis since thousands of plants need to be growth in order to get as much data as
possible. the data would have definitely been skewed if there was not a controlled
environment in which the plants could grow. In the example, a windy day would have caused
pollination via the wind which would have definitely