In flies, Red eyes are dominant to white. If a true-breeding red-eye fly bred with a true breeding white-eye fly, the offspring will be:

Answer and Explanation:

Available data:

Cross: true-breeding red-eye fly bred with a true breeding white-eye fly

Parentals)           RR           x       rr

Phenotypes) Red-eyed     White-eyed

Gametes)       R         R           r         r

Punnett square)     R          R

                       r      Rr         Rr

                       r      Rr         Rr

F1) 4/4 = 100% of the progeny will be heterozygous for the trait expressing     red eyes, Rr

In Drosophila melanogaster, the fruit fly, the gene for the eye color is X-linked. So in this species:

- X⁺ expresses red eyes > + is the dominant allele for red color

- X⁻ expresses white eyes > - is the recessive allele for white color

Option 1: true-breeding red-eyed females and white-eyed male

Parentals)                X⁺ X⁺          x       X⁻Y

Phenotypes) Red-eyed female     White-eyed male

Gametes)           X⁺            X⁺             X⁻         Y      

Punnett square)      X⁺           X⁺

                     X⁻    X⁺X⁻       X⁺X⁻

                     Y      X⁺Y         X⁺Y

F1) 4/4 = 100% of the progeny will express red eyes

    50% of individuals are red-eyed males, X⁺Y

    50% of individuals are red-eyed heterozygous females, X⁺X⁻

Option 2: true-breeding white-eyed females and red-eyed male

Parentals)                X⁻ X⁻         x       X⁺Y

Phenotypes) Red-eyed female     White-eyed male

Gametes)           X⁻            X⁻             X⁺         Y      

Punnett square)      X⁻           X⁻

                     X⁺    X⁺X⁻       X⁺X⁻

                     Y      X⁻Y         X⁻Y

F1) 2/4 = 50% of the progeny will be females expressing red eyes, X⁺X⁻

    2/4 = 50% of the progeny will be white-eyed males, X⁻Y

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.