Answer :
To determine which Punnett Square correctly represents the cross between a plant with genotype [tex]\(BB\)[/tex] and a plant with genotype [tex]\(Bb\)[/tex], we must first understand how the alleles combine.
1. Parents' Genotypes:
- One parent has genotype [tex]\(BB\)[/tex]
- The other parent has genotype [tex]\(Bb\)[/tex]
2. Gametes Produced:
- The BB parent can only contribute [tex]\(B\)[/tex] alleles.
- The Bb parent can contribute either [tex]\(B\)[/tex] or [tex]\(b\)[/tex] alleles.
3. Construct the Punnett Square:
The setup for the Punnett square would look like this:
[tex]\[ \begin{array}{c|c|c} & B & b \\ \hline B & BB & Bb \\ \hline B & BB & Bb \\ \end{array} \][/tex]
Each cell in the Punnett square represents a possible combination of alleles from each parent. The possible genotypes of the offspring are:
- Upper left cell: [tex]\(BB\)[/tex]
- Upper right cell: [tex]\(Bb\)[/tex]
- Lower left cell: [tex]\(BB\)[/tex]
- Lower right cell: [tex]\(Bb\)[/tex]
4. Evaluate Given Options:
Option A:
[tex]\[ \begin{array}{|c|c|c|} \hline & b & b \\ \hline & Bb & Bb \\ \hline & bb & bb \\ \hline \end{array} \][/tex]
- This option incorrectly includes [tex]\(bb\)[/tex] genotypes, which are not possible from a cross of [tex]\(BB \times Bb\)[/tex].
Option B:
[tex]\[ \begin{array}{|c|c|} \multicolumn{1}{c}{} & \multicolumn{1}{|c|}{} \\ \hline B & b \\ \hline BB & Bb \\ \hline BB & Bb \\ \hline \end{array} \][/tex]
- This option correctly represents the possible offspring genotypes: [tex]\(BB\)[/tex] and [tex]\(Bb\)[/tex].
Option C:
[tex]\[ \begin{array}{|c|c|c|} \hline & B & b \\ \hline & Bb & Bb \\ \hline & Bb & Br \\ \hline \end{array} \][/tex]
- This option incorrectly includes a genotype [tex]\(Br\)[/tex], which is not valid with the given alleles.
Option D:
[tex]\[ \begin{array}{|c|c|c|} \hline & B & b \\ \hline & BB & Bb \\ \hline 0 & BB & Bb \\ \hline \end{array} \][/tex]
- This option incorrectly includes a genotype 0, which is not valid.
Therefore, the correct representation of this cross in a Punnett Square is:
Option B:
[tex]\[ \begin{array}{|c|c|} \multicolumn{1}{c}{} & \multicolumn{1}{|c|}{} \\ \hline B & b \\ \hline BB & Bb \\ \hline BB & Bb \\ \hline \end{array} \][/tex]
The correct option is 2.
1. Parents' Genotypes:
- One parent has genotype [tex]\(BB\)[/tex]
- The other parent has genotype [tex]\(Bb\)[/tex]
2. Gametes Produced:
- The BB parent can only contribute [tex]\(B\)[/tex] alleles.
- The Bb parent can contribute either [tex]\(B\)[/tex] or [tex]\(b\)[/tex] alleles.
3. Construct the Punnett Square:
The setup for the Punnett square would look like this:
[tex]\[ \begin{array}{c|c|c} & B & b \\ \hline B & BB & Bb \\ \hline B & BB & Bb \\ \end{array} \][/tex]
Each cell in the Punnett square represents a possible combination of alleles from each parent. The possible genotypes of the offspring are:
- Upper left cell: [tex]\(BB\)[/tex]
- Upper right cell: [tex]\(Bb\)[/tex]
- Lower left cell: [tex]\(BB\)[/tex]
- Lower right cell: [tex]\(Bb\)[/tex]
4. Evaluate Given Options:
Option A:
[tex]\[ \begin{array}{|c|c|c|} \hline & b & b \\ \hline & Bb & Bb \\ \hline & bb & bb \\ \hline \end{array} \][/tex]
- This option incorrectly includes [tex]\(bb\)[/tex] genotypes, which are not possible from a cross of [tex]\(BB \times Bb\)[/tex].
Option B:
[tex]\[ \begin{array}{|c|c|} \multicolumn{1}{c}{} & \multicolumn{1}{|c|}{} \\ \hline B & b \\ \hline BB & Bb \\ \hline BB & Bb \\ \hline \end{array} \][/tex]
- This option correctly represents the possible offspring genotypes: [tex]\(BB\)[/tex] and [tex]\(Bb\)[/tex].
Option C:
[tex]\[ \begin{array}{|c|c|c|} \hline & B & b \\ \hline & Bb & Bb \\ \hline & Bb & Br \\ \hline \end{array} \][/tex]
- This option incorrectly includes a genotype [tex]\(Br\)[/tex], which is not valid with the given alleles.
Option D:
[tex]\[ \begin{array}{|c|c|c|} \hline & B & b \\ \hline & BB & Bb \\ \hline 0 & BB & Bb \\ \hline \end{array} \][/tex]
- This option incorrectly includes a genotype 0, which is not valid.
Therefore, the correct representation of this cross in a Punnett Square is:
Option B:
[tex]\[ \begin{array}{|c|c|} \multicolumn{1}{c}{} & \multicolumn{1}{|c|}{} \\ \hline B & b \\ \hline BB & Bb \\ \hline BB & Bb \\ \hline \end{array} \][/tex]
The correct option is 2.
