To determine the phenotype ratio for the given cross, first understand the contributions of each parent.
1. Identify Genotypes of Parents:
- The first parent contributes two alleles: [tex]$t$[/tex] and [tex]$t$[/tex].
- The second parent contributes two alleles: [tex]$T$[/tex] and [tex]$t$[/tex].
2. Set Up the Punnett Square:
- Label the Punnett square with the alleles of each parent:
[tex]\[
\begin{array}{|c|c|c|}
\hline
& T & t \\
\hline
t & Tt & tt \\
\hline
t & Tt & tt \\
\hline
\end{array}
\][/tex]
3. Determine Genotypes in Each Box:
- The top left box results from [tex]$t$[/tex] (from the first parent) and [tex]$T$[/tex] (from the second parent); the genotype is [tex]$Tt$[/tex].
- The top right box results from [tex]$t$[/tex] (from the first parent) and [tex]$t$[/tex] (from the second parent); the genotype is [tex]$tt$[/tex].
- The bottom left box results from [tex]$t$[/tex] (from the first parent) and [tex]$T$[/tex] (from the second parent); the genotype is [tex]$Tt$[/tex].
- The bottom right box results from [tex]$t$[/tex] (from the first parent) and [tex]$t$[/tex] (from the second parent); the genotype is [tex]$tt$[/tex].
4. Summarize the Genotypes:
- We have two [tex]$Tt$[/tex] (short tails) and two [tex]$tt$[/tex] (long tails).
5. Convert Genotypes to Phenotypes:
- [tex]$Tt$[/tex] results in a short tail because the short tail allele ([tex]$T$[/tex]) is dominant.
- [tex]$tt$[/tex] results in a long tail because there are only recessive alleles.
6. Phenotype Ratio:
- We have 2 short tails ([tex]$Tt$[/tex]) and 2 long tails ([tex]$tt$[/tex]).
- Therefore, the phenotype ratio is 2 short tails : 2 long tails.
Consequently, the phenotype ratio for this cross is:
D. 2 long, 2 short
