drosophila eye color is an x - linked trait. red eye color is dominant, and white eye color is recessive…

drosophila eye color is an x - linked trait. red eye color is dominant, and white eye color is recessive. which punnett square shows a cross in which the probability of offspring will have red eyes is 100 percent?

drosophila eye color is an x - linked trait. red eye color is dominant, and white eye color is recessive. which punnett square shows a cross in which the probability of offspring will have red eyes is 100 percent?

Answer

Explanation:

Step1: Recall X - linked inheritance rules

In X - linked inheritance, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). Red eye color ($X^R$) is dominant and white eye color ($X^r$) is recessive. For all offspring to have red eyes, both parents must contribute at least one $X^R$ allele.

Step2: Analyze each Punnett - square

  • In the first Punnett - square, both parents are $X^r$, so all offspring will have white eyes.
  • In the second Punnett - square, one parent is $X^R$ and the other is $X^r$. Some offspring may get $X^r$ and have white eyes.
  • In the third Punnett - square, similar to the second, some offspring may get $X^r$ and have white eyes.
  • In the fourth Punnett - square, one parent is $X^R$ and the other is also $X^R$. All female offspring will be $X^R X^R$ or $X^R X^r$ and all male offspring will be $X^R Y$, so all offspring will have red eyes.

Answer:

The fourth Punnett - square (where one parent is $X^R$ and the other is $X^R$) shows a cross in which the probability of offspring having red eyes is 100 percent.