To determine which two statements about the genotype of the plants' stem lengths are true, we need to carefully analyze the information given in the Punnett squares.
### First Generation Punnett Square
[tex]\[
\begin{tabular}{|c|c|c|}
\hline
First Generation & [tex]$t$[/tex] & [tex]$t$[/tex] \\
\hline
[tex]$T$[/tex] & [tex]$Tt$[/tex] & [tex]$Tt$[/tex] \\
\hline
[tex]$T$[/tex] & [tex]$Tt$[/tex] & [tex]$Tt$[/tex] \\
\hline
\end{tabular}
\][/tex]
In the first generation Punnett square, all the offspring (both inside the square's cells) have the genotype \( Tt \). This shows that both \( T \) (tall allele) and \( t \) (short allele) are present in the offspring. The dominant allele \( T \) makes these plants tall because it masks the presence of the recessive \( t \) allele.
### Second Generation Punnett Square
[tex]\[
\begin{tabular}{|c|c|c|}
\hline
Second Generation & [tex]$T$[/tex] & [tex]$t$[/tex] \\
\hline
[tex]$T$[/tex] & [tex]$TT$[/tex] & [tex]$Tt$[/tex] \\
\hline
[tex]$t$[/tex] & [tex]$Tt$[/tex] & [tex]$tt$[/tex] \\
\hline
\end{tabular}
\][/tex]
In the second generation Punnett square:
- One cell has genotype \( TT \) (homozygous tall)
- Two cells have genotype \( Tt \) (heterozygous tall)
- One cell has genotype \( tt \) (homozygous short)
### Analyzing Statements
1. Plants with short stems are homozygous for that trait.
- True. The only way for a plant to have a short stem is to have the \( tt \) genotype, which is homozygous recessive.
2. Plants with tall stems are always homozygous for that trait.
- False. Plants with tall stems can have the genotype \( TT \) (homozygous) or \( Tt \) (heterozygous). The dominant \( T \) allele ensures they are tall in both cases.
3. Both parent plants in the second generation are heterozygous.
- False. The parent plants used to make the Punnett square in the second generation are \( Tt \) and \( Tt \), which are heterozygous. However, the statement's wording is ambiguous as it says "in second generation" which might imply offspring, not parents.
4. Both parent plants in the second generation are homozygous.
- False. The parent plants in the second generation Punnett square are heterozygous, not homozygous.
### Conclusion
The two true statements are:
- Plants with short stems are homozygous for that trait.
- Both parent plants in second generation are heterogenous.
