GENETICS AND EVOLUTION
GENETIC BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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all intermediate forms
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all tall
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all dwarf
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1/2 tall, 1/2 dwarf
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3/4 tall, 1/4 dwarf
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Detailed explanation-1: -Answer and Explanation: If the two heterozygous plants (Dd) crossed, the offspring would be 3/4 tall, 1/4 dwarf. Therefore, the correct answer is option d). Generally, when a cross between the two heterozygous parents produces the offspring with a 3:1 phenotypic ratio.
Detailed explanation-2: -In one of the experiments with pea plants, Mendel observed that when a homozygous tall pea plant (TT) is crossed with a homozygous dwarf pea plant (tt), in the first generation, only tall plants appear.
Detailed explanation-3: -In a cross between heterozygous tall plants (Tt) and a homozygous dwarf plant (tt), the ratio in the offspring shall be 1 tall : 1 dwarf. This is because the heterozygous plant will make two types of gametes, one type having T allele and the other having t allele.
Detailed explanation-4: -The selfing of heterozygous tall plants yields F2 generation with the genotypic ratio of 1 TT (homozygous tall): 2 Tt (heterozygous tall): 1 tt (homozygous dwarf). Thus, the correct answer is option B.
Detailed explanation-5: -What is the phenotypic ratio of the offspring? The phenotypic ratio will be 1 tall:1 dwarf.