The Australian grass tree, from the genus Xanthorrhoea in the lily family, grows to a height of about 4.5 m, bears long narrow leaves in a tuft at the top of the trunk, and produces yellow or white flowers in a spike above the leaves. A yellow-flowered tree was test-crossed. The seeds were collected and planted. The resulting progeny were 28 white-flowered trees and 23 yellow-flowered trees.
What is the expected phenotypic ratio of white-flowering grass trees to yellow-flowering grass trees among the progeny that result from the cross?
Enter your answer in the format yellow:white (for example you would enter 10:3 if you expect that that the phenotypic ratio should be 10 yellow-flowering trees for every 3 white flowering trees).
what is the ratio
1:2
To determine the expected phenotypic ratio of white-flowering grass trees to yellow-flowering grass trees among the progeny, we can use the principles of Mendelian genetics.
In this case, we have a test-crossed yellow-flowered tree. This means that the tree being tested has a genotype of "yy" (since yellow is the dominant trait) and is being crossed with another tree that is white-flowered and has a genotype of "yy" (since white is the recessive trait).
When two individuals with genotype "yy" are crossed, all of their offspring will have the genotype "yy". Therefore, all the progeny will exhibit the yellow-flowering phenotype.
Therefore, the expected phenotypic ratio of white-flowering grass trees to yellow-flowering grass trees among the progeny is 0:51 or simply 0 yellow-flowering trees for every 51 white-flowering trees.