In tomatoes, the allele T for tall plant height is dominant to allele t, the P a

ID: 61755 • Letter: I

Question

In tomatoes, the allele T for tall plant height is dominant to allele t, the P allele for smooth skin is dominant to P allele for peach fuzz skin, and the allele R for round fruit is dominant to the recessive r allele for oblong fruit, e genes controlling these traits are linked on chromosome 1 in the tomato genome, and the genes are arranged in the order and with the recombination frequencies shown. Gene T P R Recombination frequency 0.04 0.18 A pure-breeding tall, peach fuzz, round plant is crossed to a pure-breeding plant that is dwarf, smooth, oblong. What are the gamete genotypes produced by each of these plants? What are the genotype and phenotype of the F: progeny of this cross? What are the genotypes of gametes produced by the F1, and what is the predicted frequency of each gamete? The F1 are test-crossed to dwarf, peach fuzz, oblong Plants, and 1000 test-cross progeny are produced. What are the phenotypes of test-cross progeny, and what number of progeny is expected in each class?

Explanation / Answer

TTppRR x ttPPrr

The gametes produced from these plants are TpR and tPr.

TpR x tPr

All the F1 progeny will have the same genotype TtpPRr, with the phenotype being tall plant, smooth skinned, round fruit.

TtpPRr x TtpPRr

The genotypes of the gametes produced by these plants are as follows:

TpR, Tpr, TPR, TPr, tpR, tpr, tPR, and tPr

The predicted frequency of each of these gametes is 1/8.

When F1 are test crossed to dwarf, peach fuzz, oblong plants, the following progeny are obtained in respective percentages with respective phenotypes.

TtppRr – 12.5% - tall, peach, round

Ttpprr – 12.5% - tall, peach, oblong

TtPpRr – 12.5% - tall, smooth, round

TtPprr – 12.5% - tall, smooth, oblong

ttppRr – 12.5% - dwarf, peach, round

ttpprr – 12.5% - dwarf, peach, oblong

ttPpRr – 12.5% - dwarf, smooth, round

ttPprr – 12.5% - dwarf, smooth, oblong

Out of 64 progeny, each genotype has occupied 8 plants; and then out of 1000 progeny, each genotype would occupy 125 plants.

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In tomatoes, the allele T for tall plant height is dominant to allele t, the P a

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