Imagine that a couple is planning to have children. The male is heterozygous for tongue rolling and homozygous dominant for unattached earlobes. The female is homozygous recessive for tongue rolling and heterozygous for unattached earlobes. The couple is curious about the possibility and probability of their offspring inheriting these traits. The ability to roll ones tongue is dominant (R) over the “non-rolling” condition (r.) Unattached earlobes (U) are dominant over attached earlobes (u) Complete a Punnett square for this cross and record the probabilities for genotypes and phenotypes of the offspring as ratios.

F1 generation:         RrUu, rrUU, rrUu, RrUU

                               25% : 25%: 25%: 25%

Ratios

Explanation:

Punnett squares are a diagrammatic way of deciding the characteristics of hybrid offspring created by crosses in genetic breeding. Parental genotypes and phenotypes are widely recognized, and all usually obey normal Mendelian ratios and inheritance.

Mendelian genetics focuses on the origin or heritability of characteristics. Such traits are packed into one's own gamete, acquired by themselves, and sometimes display superiority, where one's impact can mask those of another trait.

These are called the Law of Segregation, Independent assortment and Dominance respectively.

For this cross...  Assuming:

Unattached lobes= dominant

Gametes:

R → rolling dominant (R), non-rolling recessive (r)

U → unattached dominant (U), attached recessive (u)

P generation:                          RUrU× rUru

                       rolling, unattached  × non-rolling, unattached

F1 generation:         RrUu, rrUU, rrUu, RrUU

                               25% : 25%: 25%: 25%

Ratios

Half the offspring have unattached lobes and can roll their tongues while the other half have unattached lobes and cannot roll their tongues...

Each punnet cross is attached below

option c is the correct answer.