In tomatoes, tall is dominant to dwarf, and smooth fruits are dominant to hairy fruits.A plant homozygous for both dominant traits is crossed with a plant homozygous for both recessive traits.The F₁ progeny are crossed with a homozygous recessive, with the results shown in the table. These data indicate that the genes are A) on different chromosomes. B) linked and show 5 percent recombination. C) linked and show 10 percent recombination. D) linked and show 20 percent recombination. E) linked and show 40 percent recombination.

Question

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The table shows 100 offspring, 89 of which have the dominant tall and smooth traits, 3 of which have the recessive dwarf and hairy traits, and 8 of which have a combination of traits that are different from both parents. The fact that some offspring have new combinations of traits that were not present in either parent indicates that the genes are linked, because if they were on different chromosomes, independent assortment would have resulted in a larger proportion of offspring with either the dominant or recessive traits. The frequency of the new combinations (8/100) indicates a recombination frequency of 8%, which corresponds to 10% map distance (because the genetic map is based on double the recombination frequency, since only one of two linked genes can undergo recombination in a heterozygous individual). Therefore, the best answer is C, linked and show 10 percent recombination.

In Tomatoes, Tall Is Dominant to Dwarf, and Smooth Fruits