When a red eyed homozygous female Drosophila is crossed with a white eyed male the phenotype of progeny in the f1 generation will be?

In his initial test cross aimed at exploring the precise relationship between eye color and sex, Morgan bred white-eyed males (XwY) with wild-type red-eyed females (X+X+). This cross yielded only red-eyed offspring, as summarized in Table 3.

Table 3: Morgan's First Test Cross

    Male Gametes
    Xw Y
Female Gametes X+ X+Xw X+Y

X+

X+Xw

X+Y

Next, Morgan decided to cross two flies from the F1 generation—specifically, a red-eyed female (X+Xw) and a red-eyed male (X+Y)—to test for a recessive pattern of inheritance. This cross is depicted in Table 4.

Table 4: Morgan's Second Test Cross

    Male Gametes
    X+ Y
Female Gametes X+ X+X+ X+Y
Xw X+Xw XwY

As shown in the table, the offspring of this cross exhibited a 3:1 ratio of red eyes to white eyes, which indicated that white eyes were recessive. Moreover, all of the white-eyed F2 offspring were male.

Next, as previously discussed, Morgan conducted a third cross to determine whether white eyes were lethal in female flies. Here, he bred red-eyed females (X+Xw) with white-eyed males (XwY), as summarized in Table 5.

Table 5: Morgan's Third Test Cross

    Male Gametes
    Xw Y
Female Gametes X+ X+Xw X+Y
Xw XwXw

XwY

This third cross revealed that white eyes were in fact not lethal in females, because it produced a 1:1:1:1 ratio of red-eyed females to white-eyed females to red-eyed males to white-eyed males.

Finally, Morgan opted to conduct a fourth cross to determine whether the white-eye trait followed the inheritance of the X chromosome from maternal gametes to male offspring. This reciprocal F1 cross was the most crucial part of this series of experiments, because Morgan could make some very concrete predictions if the trait was indeed sex-linked. Specifically, because the white-eyed trait appeared to be recessive, Morgan could predict that a white-eyed female would probably be homozygous recessive. Moreover, because males inherit their only X chromosome from their mother, the use of a white-eyed mother would mean that an X-linked white-eyed trait would be the only trait male flies could inherit from a homozygous mother. Thus, Morgan could predict that all male offspring resulting from a cross between a white-eyed female and a red-eyed male would be white eyed. Likewise, because female offspring inherit the only X chromosome that exists in the paternal gametes, all female offspring of this particular cross would carry the red-eye trait, and this trait would mask the recessive white-eye trait they inherited via the maternal gametes.

To test these predictions, Morgan crossed a white-eyed female with a red-eyed male, as depicted in Table 6.

Table 6: Morgan's Fourth Test Cross

    Male Gametes
    X+ Y
Female Gametes Xw X+Xw XwY
Xw X+Xw

XwY

Because this cross yielded all white-eyed males and all red-eyed females, Morgan could indeed conclude that the white-eye trait followed a sex-linked pattern of inheritance.

When red eyed males are crossed with white eyed females, one expects white eyed males and red eyed females in F 1 generation. However, Bridges found that sometimes, in such a cross, red eyed males and white eyed females could be observed. What was the reason for this observation?A. EpistasisB. CodominanceC. Non disjunction of X chromosomesD. Homologous recombination

Non-disjunction of X chromosomes

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