Genetics
Based on the resulting F1 and F2 phenotypes, the dominant allele is yellow and the recessive green. This was the only possible conclusion given that the parents were yellow and green, the F1 phenotypes were all yellow, and the 3:1 F2 ratio of yellow to green. In contrast, incomplete dominance would have resulted in yellowish-green peas.
If 'C' represents the yellow allele and 'c' the green, then the parents were CC and cc, and the F1 generation were all Cc. Since the F1 generation was all Cc and predicted to segregate in accordance with Mendelian inheritance, the predicted ratio would be 3:1 yellow-dominant.
Trait
Observed
Expected
Obs - Exp
(O-E)^
[(O-E)^2]/E
Yellow
Green
Chi Square
Sum =
When the Chi Square test was performed on the resulting numbers, the result was zero. This suggests that there was no difference between the results and the ratio predicted by Mendelian inheritance for a dominant-recessive set of two alleles.
Experiment 2
The result of crossing PP and pp parents, and then crossing the F1 generation with each other, revealed that the dominant allele is axial (P) and the recessive is terminal...
This conclusion is supported by getting all F1 axial flowers and an axial/terminal ratio of 3:1 for the F2 generation. If these alleles segregated according to Mendelian genetics, then the F2 generation would be predicted to result in a 3:1 ration of axial to terminal phenotypes.
Trait
Observed
Expected
Obs - Exp
(O-E)^2
[(O-E)^2]/E
Axial
75
75
0
0
0
Terminal
25
25
0
0
0
Chi Square
Sum =
0
To confirm that the axial and terminal alleles are segregating according to Mendelian genetics, a chi square test was performed on the results (see above table). The resulting chi square is zero, which means there is no difference between the results and what would be predicted according to Mendelian genetics.
If the alleles from experiments 1 and 2 were found to exist in natural world at the same ratios, then the C (yellow) and P (axial) alleles would be considered wild-type. Although many mutations result in a loss of function or expression, there are exceptions. For example, the gap-junction protein connexin…
