Corn Genetics Lab
We have some ears of corn that were produced to demonstrate Mendelian genetics.
There are many traits in corn, but in this lab we are following the inheritance
pattern of two traits controlled by one gene each. In both genes there are two
alleles and one is completely dominant over the other: P (purple pigment) is
dominant to p (yellow pigment), and S (smooth seeds) are dominant to s (wrinkled
seeds).
We can see one cob each of the true breeding parents (PPSS X ppss). As you know,
the offspring of this cross would produce an F1 consisting of all PpSs (purple and
smooth).
In one cross we can observe the F2 resulting from these F1 plants. What
phenotypes do you expect, and in what ratios?
We also have ears resulting from a test cross of a F1 (PpSs) and the true-breeding
yellow/wrinkled parent. What genotypes and phenotypes would you expect from
this cross and in what ratios?
For these two crosses we have expected phenotypic ratios, and from the ears of corn
we can see the observed outcomes. We’re going to have to share the limited number
of corn ears, so each group needs to assign kernels from 3 rows on the cob to one of
the expected phenotypes. Then for each of the crosses, we will determine the chi
square value and then determine if we accept or reject the null hypothesis.
This is not a controlled experiment, however, you should write a report that
provides an introduction to both the underlying genetics and the statistical test (chi
square) that will tell us if the departure from expected outcomes is within the range
of random chance (accept the null hypothesis), or if the observed outcomes depart
so significantly from the expected outcomes that we are compelled to reject the null
hypothesis. I expect to see all of your calculations in your report.
Introduction
Data presentation
Statistical analysis
Conclusion