In peas, the round allele is dominant over the wrinkled allele. If a plant with round peas is crossed to a plant with wrinkled peas, all of the resulting plants have round peas. What is the genotype of the parents in this cross?

A) RR × rr

B) RR × Rr

C) Rr × rr

D) Rr × Rr

E) rr × rr

a) RR x rr

Explanation:

First, we need to glean as much information as we can from the initial statement. If one of the plants is wrinkled, and ‘wrinkled’ is a recessive trait, then we know that that particular plant must have and homozygous recessive (rr) genotype. As for the other plant: Since it has a round phenotype, it may have either an ‘Rr’ (option C) or ’RR’ (option A) genotype. We may then build the corresponding Punnett charts:

Option C:

       |      r      |       r

R     |     Rr     |     Rr

r      |      rr     |      rr

Option A:

       |      r      |       r

R     |     Rr     |     Rr

R     |     Rr     |     Rr

As we can see, only option (A) will lead to the entirety of the descendants having a round phenotype.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".