A cross gives a phenotypic ratio of three tall and one dwarf. Which genotype cross best explains this result?
Answer and explanation
Correct answer: Tt cross Tt
For a single trait with complete dominance, the 3:1 phenotypic ratio is the expected result of crossing two heterozygotes. In Tt × Tt, the genotypes are TT, Tt, Tt, and tt in a 1:2:1 ratio. Three offspring show the dominant tall phenotype and one shows the recessive dwarf phenotype. TT × TT gives all tall, TT × tt gives all tall, and Tt × TT gives all tall phenotypically, so only option C fits.
Frequently asked questions
What is the correct answer to this question?
Tt cross Tt
Why is this the correct answer?
For a single trait with complete dominance, the 3:1 phenotypic ratio is the expected result of crossing two heterozygotes. In Tt × Tt, the genotypes are TT, Tt, Tt, and tt in a 1:2:1 ratio. Three offspring show the dominant tall phenotype and one shows the recessive dwarf phenotype. TT × TT gives all tall, TT × tt gives all tall, and Tt × TT gives all tall phenotypically, so only option C fits.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: World of Living. Topic: Heredity and Evolution.
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