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To understand the predicted incidence of color blindness among females in a population with a known male incidence rate of 1 in 20, it's important to consider the genetic basis of color blindness. This condition is primarily linked to the X chromosome. Males, having one X and one Y chromosome, will express color blindness if they inherit the affected X chromosome, leading to a higher prevalence among them.

In females, who have two X chromosomes, the inheritance of the condition requires that both X chromosomes carry the gene for color blindness to exhibit the trait. Therefore, the incidence in females is much lower than in males.

Given that the color blindness rate among males is 1 in 20, we can derive the rate for females using basic genetic principles. Since females have a 2:1 X chromosome advantage to be unaffected (they would need both X chromosomes to be affected), the incidence of color blindness in females would be approximately 1 in 400.

Thus, the figure 1 in 400, represents the adjusted likelihood of color blindness in females based on the relatively higher incidence in males, providing a meaningful understanding of the genetic distribution of this trait in gender-divided populations.