Explain how parents, both with dominant phenotypes, can have offspring with recessive phenotypes. Include a Punnett Square and inheritance terms (phenotype, genotype, homozygous, heterozygous, locus, allele, dominant, recessive, genotypic ratio, phenotypic ratio, P, F1, F2) in your answer.

 

When both parents have dominant phenotypes, but their alleles are heterozygous, F1 has the necessary information to produce both parental phenotypes in the next generation, since these genes are located at the same locus. When the allele is dominant, it is expressed at the expense of the alternative allele and when it is recessive, it is an allele whose expression is suppressed in the presence of a dominant allele.

For example, a woman with brown eyes color Bb marries a man with brown eyes color Bb, both parents manifest a dominant phenotype of brown eyes color but their genotype is heterozygous and has allele for the color of brown eyes "B" and other alleles for blue eye color "b", located at the same locus, with eye color being a dominant phenotype with respect to blue color, in the first filial generation it will give a 3: 1 phenotypic ratio in which the dominant characteristic It is three times more frequent than the recessive characteristic, that is, ¾ or 75% children with brown eyes of genotypes with at least one dominant character, specifically 25% ¼ BB homozygous dominant and 50% or 2/4 Bb heterozygous and the least frequent ¼ or 25% of children with homozygous recessive blue-eyed color, in this way it can be shown that both parents with dominant phenotypes can have recessive phenotype offspring, in this case blue-eyed children s. Regarding the F2 or second filial generation, this homozygous recessive offspring with blue eyes will be the one who will have the opportunity for offspring.

Step-by-step explanation

Parents (P): Bb heterozygous x Bb heterozygous

 Brown-eyed mother x Brown-eyed father

Gametes: B, b x B, b

F1

Phenotypic ratio: Genotypic ratio:

¾ or 75% brown eyes color. ¼ or 25% BB homozygous dominant, 2/4 or 50% BB heterozygous

1/4 or 25% blue eye color. ¼ or 25% bb homozygous recessive

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