Question

parents that are heterozygous for having freckles (dominant) are crossed. which correctly describes their offspring?
twenty - five percent have freckles.
twenty - five percent are ff.
seventy - five percent have freckles.
seventy - five percent are ff.

Explanation:

Step1: Set up the cross

Let F represent the dominant allele for freckles and f represent the recessive allele. Heterozygous parents have the genotype Ff. When Ff x Ff is crossed, we use a Punnett - square.

Step2: Create the Punnett - square

The possible gametes from each parent are F and f. The Punnett - square has 4 boxes. The combinations are FF, Ff, Ff, and ff.

Step3: Analyze genotypes and phenotypes

FF and Ff genotypes result in the freckled phenotype (dominant). The ratio of genotypes is 1 FF : 2 Ff : 1 ff. The ratio of phenotypes is 3 freckled (FF + Ff + Ff) : 1 non - freckled (ff).

Step4: Calculate percentages

The percentage of offspring with freckles is $\frac{3}{4}\times100\% = 75\%$, and the percentage of non - freckled offspring is $\frac{1}{4}\times100\% = 25\%$. The percentage of Ff genotype is $\frac{2}{4}\times100\% = 50\%$.

Answer:

Seventy - five percent have freckles.