Question

1. white flowers are dominant over purple flowers in pea plants. fill in the punnett square and determine the expected genotypic and phenotypic ratios from crossing homozygous recessive and homozygous recessive parents. genotypes: __________ genotypic ratio: ____ phenotypes: ________ phenotypic ratio: ______

Explanation:

Answer:

Punnett Square Filling:

Let the allele for white flower be \( W \) (dominant) and for purple flower be \( w \) (recessive). Both parents are homozygous recessive, so their genotype is \( ww \). When we set up the Punnett square, both the top row and left - hand column will have \( w \) (from each parent's gametes, since a homozygous recessive parent \( ww \) can only produce \( w \) gametes).

	\( w \)	\( w \)
\( w \)	\( ww \)	\( ww \)

Genotypes:

All the offspring will have the genotype \( ww \).

Genotypic Ratio:

Since all four cells in the Punnett square have the genotype \( ww \), the genotypic ratio is \( 4:0 \) (or simply \( 1:0 \) when simplified, but more accurately, since there are four individuals with \( ww \) and zero with other genotypes, it can be written as \( ww:WW:Ww = 4:0:0 \), but in the case of crossing two \( ww \) parents, the ratio of \( ww \) to non - \( ww \) is \( 4:0 \), or we can say the genotypic ratio is \( 100\% \) \( ww \), but in ratio terms (for the possible genotypes here, since only \( ww \) is possible), the ratio is \( 4:0 \) (or \( 1:0 \) if we consider relative to other non - existent genotypes) or more simply, since all are \( ww \), the genotypic ratio is \( ww:ww:ww:ww = 1:1:1:1 \) (but that's a bit redundant), the standard way is that the genotypic ratio is \( 4:0 \) for \( ww \) to other genotypes, or since all are \( ww \), we can say the genotypic ratio is \( 1:0 \) ( \( ww \) to non - \( ww \)). But more accurately, when crossing two homozygous recessive (\( ww\times ww \)), the genotypic ratio is \( ww:WW:Ww=4:0:0 \), which can be simplified to \( 1:0:0 \) (but usually, for this cross, we just say all offspring are \( ww \), so the genotypic ratio is \( 4:0 \) (with \( 4 \) \( ww \) and \( 0 \) of the other genotypes) or \( 1:0 \) (if we consider the ratio of \( ww \) to the sum of other genotypes).

Phenotypes:

Since the genotype is \( ww \) (recessive) and purple flowers are the recessive phenotype (because white is dominant, so \( ww \) will show the purple flower phenotype), all the offspring will have purple flowers.

Phenotypic Ratio:

Since all four offspring have purple flowers and zero have white flowers, the phenotypic ratio of purple to white flowers is \( 4:0 \) (or \( 1:0 \) when simplified, or we can say \( 100\% \) purple, but in ratio terms, purple: white \( = 4:0 \)).

Final Genotypic and Phenotypic Details:

• Genotypes: All \( ww \)
• Genotypic Ratio: \( ww:WW:Ww = 4:0:0 \) (or \( 1:0:0 \)) or more simply, since all are \( ww \), the ratio of \( ww \) to other genotypes is \( 4:0 \)
• Phenotypes: All purple flowers
• Phenotypic Ratio: Purple: White \( = 4:0 \) (or \( 1:0 \))