Question

practicing monohybrid crosses

purple petal color in pea plants is dominant to white petal color. two heterozygous pea plants are crossed.

what is the ratio of the offspring with white petals to the total number of offspring?

express this in a percentage.

Explanation:

Identify alleles and parental genotypes

Using the Punnett Square knowledge point, we define the alleles for petal color:

• \(D\): dominant allele for purple petals
• \(d\): recessive allele for white petals

Since both parent pea plants are heterozygous, their genotypes are both \(Dd\).

Set up the monohybrid cross

We cross the two heterozygous parents (\(Dd \times Dd\)) using a Punnett square:

• Parent 1 gametes: \(D\) and \(d\)
• Parent 2 gametes: \(D\) and \(d\)

The resulting offspring genotypes in the four boxes are:

1. Box 1: \(DD\) (purple petals)
2. Box 2: \(Dd\) (purple petals)
3. Box 3: \(Dd\) (purple petals)
4. Box 4: \(dd\) (white petals)

Determine the phenotypic ratio

Offspring with white petals must have the homozygous recessive genotype \(dd\).

• Number of white-petaled offspring (\(dd\)): 1 (Box 4)
• Total number of offspring: 4

The ratio of offspring with white petals to the total number of offspring is \(1:4\).

Convert the ratio to a percentage

To express the ratio \(\frac{1}{4}\) as a percentage:

$$ \frac{1}{4} \times 100\% = 25\% $$

Answer:

Purple petal color in pea plants is dominant to white petal color. Two heterozygous pea plants are crossed.

What is the ratio of the offspring with white petals to the total number of offspring?
<blank>1</blank> : <blank>4</blank>

Express this in a percentage.
<blank>25</blank>%