The kernel color in wheat is a continuous trait determined by two additive genes, each with two alleles, that equally contribute to kernel color determination. The red kernels are determined by two genes and two dominant alleles $(R_1{R}_1{R}_2{R}_2),$ and white kernels are determined by two recessive alleles at the same two genes $(r_1{r}_1{r}_2{r}_2).$ The duplicate dominant alleles $R_1$ and $R_2$ contribute equally to kernel color and cumulatively control the intensity of the red kernel phenotype. Both these alleles are dominant over the recessive white alleles $r_1$ and $r_2.$

A true breeding red plant and true breeding white plant are crossed, and the resulting $F_1$ progeny are selfed.

What is the expected phenotypic ratio of the kernel progeny of the $F_2$ offspring?

$9$:$3$:$3$:$1$

$27$:$9$:$9$:$9$:$3$:$3$:$3$:$1$

$1$:$4$:$6$:$4$:$1$

$3$:$1$

Determine which statement best describes the relationship between the phenotypes of the $r_1{r}_1{R}_2{r}_2$ and $r_1{R}_1{r}_2{r}_2$ genotypes.

The phenotype of the $r_1{r}_1{R}_2{r}_2$ will be darker than the phenotype of $r_1{R}_1{r}_2{r}_2$ because the alleles $r_1{r}_1{R}_2{r}_2$ have a stronger additive effect than those in $r_1{R}_1{r}_2{r}_2.$

There is no way to predict the expected phenotype color from the genotypes because the trait is continuous and indiscrete.

The phenotypes of the $r_1{r}_1{R}_2{r}_2$ and $r_1{R}_1{r}_2{r}_2$ genotypes will be the same because the same number of dominant and recessive alleles are contributing in each genotype.

$$ The phenotype of the $r_1{r}_1{R}_2{r}_2$ will be lighter than the phenotype of $r_1{R}_1{r}_2{r}_2$ because the alleles $r_1{r}_1{R}_2{r}_2$ have a stronger additive effect than those in $r_1{R}_1{r}_2{r}_2.$