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Pretest: Heredity

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A particular plant has two alleles that control the length of its stem. [tex]T[/tex] represents the dominant allele that codes for a tall stem, and [tex]t[/tex] represents the recessive allele that codes for a short stem. Based on the Punnett squares, which two statements are true about the genotype of the plant's stem length?

[tex]\[
\begin{tabular}{|c|c|c|}
\hline
First Generation & t & t \\
\hline
T & Tt & Tt \\
\hline
T & Tt & Tt \\
\hline
\end{tabular}
\][/tex]

[tex]\[
\begin{tabular}{|c|c|c|}
\hline
Second Generation & T & t \\
\hline
T & TT & Tt \\
\hline
t & Tt & tt \\
\hline
\end{tabular}
\][/tex]

- Plants with short stems are homozygous for that trait.
- Plants with tall stems are always homozygous for that trait.
- Both parent plants in the second generation are heterozygous.



Answer :

GinnyAnswer
To solve this question, we will analyze the given information and the genotype combinations from the Punnett squares.

### First Generation Punnett Square
Given the first generation Punnett square:
[tex]\[ \begin{array}{|c|c|c|} \hline & t & t \\ \hline T & Tt & Tt \\ \hline T & Tt & Tt \\ \hline \end{array} \][/tex]

- The first generation involves a cross between a plant with genotype [tex]\( Tt \)[/tex] and another plant with genotype [tex]\( Tt \)[/tex].
- The possible offspring genotypes are: [tex]\( Tt, Tt, Tt, Tt \)[/tex] (each entry in the table).

### Second Generation Punnett Square
Given the second generation Punnett square:
[tex]\[ \begin{array}{|c|c|c|} \hline & T & t \\ \hline T & TT & Tt \\ \hline t & Tt & tt \\ \hline \end{array} \][/tex]

- The second generation involves crossing two heterozygous plants ([tex]\( Tt \)[/tex] and [tex]\( Tt \)[/tex]).
- The possible offspring genotypes are shown in the table: [tex]\( TT, Tt, Tt, tt \)[/tex].

From the analysis of the Punnett squares:

1. Plants with short stems are homozygous for that trait.
- Short stems occur in plants that have the genotype [tex]\( tt \)[/tex] (recessive homozygous).

2. Both parent plants in the second generation are heterozygous.
- In the second generation square, both parent plants have the genotype [tex]\( Tt \)[/tex].

After examining the Punnett squares and understanding the concepts of Mendelian inheritance (dominant and recessive alleles), we can conclude that the true statements about the genotype of the plant's stem length are:

1. Plants with short stems are homozygous for that trait. [tex]\(\checkmark\)[/tex]
2. Both parent plants in the second generation are heterozygous. [tex]\(\checkmark\)[/tex]

These are the correct statements based on the analysis.

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