By: Aanand Bajaj and Mrunal Patel Task Goals: to investigate corn genetics to use a statistical test (Chi-square: 2) to determine match of theoretical and actual values
Procedure:
1. View two corn samples A and B (dihybrid). Count and record in Table 1 the number of kernels of each phenotype.
The purple color is produced by a pigmented layer within the grains. If the layer is not pigmented (colorless), the yellow color of an inner tissue shows through. Sweet corn grains wrinkle upon drying while starchy grains remain smooth. Individual kernels may be; purple—starchy (A) purple—sweet (B) yellow—starchy (C) yellow—sweet (D)
Table 1: Dihybrid Corn Kernel Count
Ear
Purple—Starchy
Purple—Sweet
Yellow—Starchy
Yellow—Sweet
Total number of kernels
A
82
293
35
85
495
B
60
223
33
111
427
Total (A+B)
142
516
68
196
922
2. Indicate the dominant traits (colour and texture). How do you know? Explain your answer.
The purple color is dominant over yellow color, and the sweet is dominant over starchy. We know this because our observations showed that the most common color for kernels was purple, and the most common kernel type was sweet.
3. Show the cross between a homozygous dominant and homozygous recessive individual for both traits.
P= Purple color p = Yellow color PPSS X ppss PPSS possible gametes: PS, PS, PS, PS S= Sweet s = Starchy ppss possible gametes: ps, ps, ps, ps
Punett Square:
ps
PS
PpSs
Therefore, the cross between a homozygous dominant (PPSS) and homozygous recessive (ppss) individual will result a dihyibrid offspring with the genotype PpSs and the phenotype of Purple color and Smooth texture.
4. Complete a cross to represent the F2 generation.
PpSs x PpSs
PpSs possible gametes: PS, Ps, pS, ps
PpSs possible gametes: PS, Ps, pS, ps
Punnett Square
If the trait is dihybrid, then out of 922 kernels, 173 will be Purple starchy, 518 will be purple sweet, 58 will be yellow starchy, and 173 will be yellow sweet.
