Question

In cabbage butterflies, white wings are dominant to yellow wings. A student completes a Punnett square showing the cross between two heterozygous butterflies. What do the letters in each of the four inside boxes tell the student?

1) The possible combinations of alleles of the offspring from the two parents
2) That both parents show the recessive trait
3) The number of offspring that the butterflies will have
4) The pedigree of the butterflies

Answer 1

The letters inside the boxes of a Punnett square represent the potential allele combinations of offspring from two heterozygous parents, predicting genotypic ratios and approximate phenotypic ratios based on dominant and recessive traits.

Step-by-step explanation:

The letters in each of the four inside boxes of a Punnett square tell the student the possible combinations of alleles of the offspring from the two heterozygous parents. If we consider the example of cabbage butterflies, where white wings are dominant (B) to yellow wings (b), and the parents are both heterozygous (Bb), the Punnett square will show a combination of alleles such as BB, Bb, bB, and bb.

These combinations demonstrate the genotypic ratios, and from this, the phenotypic ratios can be inferred. If the dominance relationship is known, three out of four of the offspring, or approximately 75%, are expected to express the dominant phenotype (white wings in this case), while one out of four, or 25%, will express the recessive phenotype (yellow wings).