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