Patterns of Inheritance I

Objectives :

1) To understand how the alleles are inherited in F1 and F2 generation of monohybrid and dihybrid crosses.

2) To determine the number of corn kernels with different phenotypes on different ears of corn.

3) To determine the ratio of corn kernels of different phenotypes in each ear of corn.

4) To determine the type of inheritance pattern in each ear of corn.

Materials :

Carolina corn dihybrid cross set, Carolina R and Su alleles 1:1:1:1 corn, Carolina C colour alleles 3:1 corn, Carolina R and Su alleles 9:3:3:1 corn, Carolina Pr and R alleles 9:3:4 corn

Methods :

Part 1 : Determination of the ratio of red and white corn kernels of a monohybrid cross

An ear of corn labeled WW-17-6520 (an F2 ear resulting from a P1 with the genotype of C/C and c/c) is given. Trait of corn kernel colour is determined by allele C. Five rows of kernel is randomly chosen from the ear of corn and the number of red and white kernels in the rows chosen are counted. The ratio of red and white kernels is determined.

Part 2 : Demonstration of dihybrid cross and ratio of purple starchy, purple sweet, yellow starchy and yellow sweet corn kernels of a dihybrid cross.

An ear of corn labeled WW-17-6600 (an F2 ear from corn sample 17-6900 with parent genotypes R/R Su/Su x r/r su/su) is given. Trait of corn kernel colour is determined by allele R and endosperm texture is determined by allele S. Five rows of kernel is randomly chosen from the ear of corn. The number of purple starchy, purple sweet, yellow starchy and yellow sweet kernels in the rows chosen are counted. The ratio of the four phenotypes is determined.

Part 3 : Determination of the ratio of purple starchy, purple sweet, yellow starchy and yellow sweet corn kernels of a dihybrid cross.

An ear of corn labeled WW-17-6602 (result of testcross between F1 hybrid with recessive parent with genotype R/r Su/su x r/r su/su) is given. Trait of corn kernel colour is determined by allele R and endosperm...