Passage I The figure below is a pedigree that shows the inheritance of a trait, Trait G, in a family. The presence of Trait G in an individual is determined entirely by Gene G. Gene G has 2 alleles: G, which is dominant, and g, which is recessive. Each individual represented in the pedigree was assigned a number (shown below the symbol for the individual) for reference. Scientists determined that the Gene G genotype of Individual 20 is gg and that the Gene G genotype of Individual 21 is Gg. Based on this information, the scientists concluded that Trait G is a recessive trait. Suppose that Individual 23 and Individual 24 have 4 biological children. Based on the figure, how many of the children, if any, have Trait G?

Correct answer: D. 4

A. 0
B. 1
C. 3
D. 4

Explanation

The best answer is D. In order to answer this item, the examinee must know how to work a genetic cross. According to the figure, both Individuals 23 and 24 have Trait G. According to the passage, Trait G is recessive. It follows that Individuals 23 and 24 both have the gg genotype and that all their children will also have the gg genotype. All their children will therefore have Trait G.

Last updated 3 September 2026

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