Question

What is the answer to this Dihybrid Crosses question? Thanks!

Answer 1

In this case, we have a double-cross between a dominant homozygous for both traits and a recessive heterozygous. According to the exercise we have red for dominant (R) white for recessive (w), tal dominant (T), and short recessive (t). So the parents are as follows

Red tall homozygous (RRTT)

White tal heterozygous (wwTt)

We obtain gametes for each parent

`\begin{gathered} R\begin{cases}T=RT \\ T=RT\end{cases}R\begin{cases}T=RT \\ T=RT\end{cases} \\ \text{these are the gametes for dominant homozygous } \\ w\begin{cases}T=wT \\ t=wt\end{cases}w\begin{cases}T=wT \\ t=wt\end{cases} \\ \text{these are the gamete for recessive htereozygous} \end{gathered}`

Now we obtain the punnet square

Now we obtain frequencies

Genotypes:

Red heterozygous tall homozygous RwTT: 8/16= 50%

Red heterozygous tall heterozygous RwTt: 8/16= 50%

Phenotypes:

Red tall 16/16=100%

Now the gardener would never obtain red short flowers because there is none recessive homozygous for height trait.