In order to understand the genotypes of the plant's stem lengths, let's analyze the Punnett squares provided. The two generations give us insights into how the alleles are distributed among the offspring.
First Generation:
[tex]\[
\begin{array}{|c|c|c|}
\hline
& t & t \\
\hline
T & Tt & Tt \\
\hline
T & Tt & Tt \\
\hline
\end{array}
\][/tex]
- The parents both contribute T and t alleles.
- The possible genotypic combination for the offspring are \( Tt \) (tall stem because the dominant allele \( T \) is present).
Second Generation:
[tex]\[
\begin{array}{|c|c|c|}
\hline
& T & t \\
\hline
T & TT & Tt \\
\hline
t & Tt & tt \\
\hline
\end{array}
\][/tex]
- One parent contributes T and t alleles (heterozygous Tt), and the other parent contributes T and T alleles (homozygous dominant TT).
- The genotypic combinations for the offspring are: \( TT \) (tall stem), \( Tt \) (tall stem), and \( tt \) (short stem).
Statements to determine correctness:
1. Plants with short stems are homozygous for that trait.
- True. The only genotype for short stems is \( tt \). This means plants with short stems must possess two recessive alleles \( tt \), making them homozygous recessive.
2. Plants with tall stems are always homozygous for that trait.
- False. Plants with tall stems can either be \( TT \) (homozygous dominant) or \( Tt \) (heterozygous). So, tall stemmed plants aren't always homozygous.
3. Both parent plants in the second generation are heterozygous.
- False. In the second generation Punnett square, the parents' genotypes are \( TT \) and \( Tt \). Therefore, it is incorrect to say both are heterozygous as one is homozygous dominant \( TT \).
4. Both parent plants in second generation are homozygous.
- False. Again, the second generation includes one homozygous dominant \( TT \) and one heterozygous \( Tt \) parent. Hence, it is incorrect to say both are homozygous.
Given this analysis, the two true statements are:
1. Plants with short stems are homozygous for that trait.
