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The genes for the trails that Mendel worked with are either all located on different chromosomes or behave as if they were. How did this help Mendel recognize the principle of independent assortment?
a. Otherwise, his dihybrid crosses would not have produced a 9:3:3:1 ratio of F2
b. The occurrence of individuals with unexpected phenotypes led him to the discovery of recombination.
c. It led him to the realization that the behavior of chromosomes during meiosis explained his results.
d. It meant that the alleles involved were either dominant or recessive, which gave 3:1 ratios in the F1 generation.
Introduction:
The principle of independent assortment states that the genes coding for different traits is passed on to the next generation independent of each other. This law of independence assortment holds true only in the case where the two pairs of characters are coded by genes that are present on two different chromosomes.
Answer to Problem 1TYK
Correct answer:
In case the genes for the trait would have been on the same chromosome, the ratio in the F2 generation would have been other than 9:3:3:1.
Explanation of Solution
Explanation/Justification for the correct answer:
Option (a) is given as the pairs are independently assorted the progeny can have different phenotypes. In case the genes are present on the same chromosome, they might show some degree of linkage. Furthermore, the presence of the genes on the same chromosome would have resulted in crossing over and alteration of the ratio of the F2 generation. Hence, Option (a) is correct.
Explanation for incorrect answers:
Option (b) is given as the discovery of the recombination as a result of the occurrence of the individuals with unexpected phenotypes. However, the process of recombination was discovered by the experiments conducted by Thomas Hunt Morgan and his colleagues on Drosophila. So, this is the wrong answer.
Option (c) is given as the results obtained during meiosis were due to the behavior of chromosomes. Mendel believed that the determinants of heredity never show blending and never gets modified. So, this is the wrong answer.
Option (d) is given as the 3:1 ratio in the F1 generation signifying that the alleles involved were either dominant or recessive. The principle of the independent assortment was introduced because of the dihybrid cross. So, this is the wrong answer.
Hence, options (b), (c), and (d) are incorrect.
Thus, the location of the chromosomes for the genes with which Mendel worked resulted in the unexpected phenotypes that helped him in recognizing the principle of independent assortment.
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Chapter 14 Solutions
Biological Science (6th Edition)
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