A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:

Which phenotypes are dominant, and which are recessive? Why?

검증된 단계별 안내

Step 1: Analyze the F₁ generation results. The F₁ generation plants all have white seeds and are tall. This indicates that the alleles for white seeds and tall stature are dominant, as these traits are expressed in the heterozygous F₁ plants.

Step 2: Examine the F₂ generation results. The F₂ generation shows a phenotypic ratio for seed color and plant stature. The phenotypes are distributed as follows: 97 blue seed, tall plant; 270 white seed, tall plant; 33 blue seed, short plant; and 100 white seed, short plant.

Step 3: Determine the inheritance pattern for seed color. The F₂ generation includes both white and blue seeds. Since white seeds appear more frequently (270 + 100 = 370) compared to blue seeds (97 + 33 = 130), white seed color is dominant, and blue seed color is recessive.

Step 4: Determine the inheritance pattern for plant stature. The F₂ generation includes both tall and short plants. Since tall plants appear more frequently (97 + 270 = 367) compared to short plants (33 + 100 = 133), tall stature is dominant, and short stature is recessive.

Step 5: Conclude the dominance relationships. White seed color and tall stature are dominant traits because they appear in the F₁ generation and are more frequent in the F₂ generation. Blue seed color and short stature are recessive traits because they are less frequent in the F₂ generation and do not appear in the F₁ generation.

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Dominant and Recessive Traits

In genetics, dominant traits are those that are expressed in the phenotype even when only one copy of the allele is present, while recessive traits require two copies of the allele to be expressed. In this scenario, the tall plant phenotype and white seed color are dominant traits, as they appear in the F₁ generation and are more prevalent in the F₂ generation.

Mendelian Inheritance

Mendelian inheritance refers to the patterns of inheritance first described by Gregor Mendel, which include the principles of segregation and independent assortment. These principles explain how alleles segregate during gamete formation and how different traits are inherited independently, allowing for the prediction of phenotypic ratios in offspring, as seen in the F₂ generation.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different phenotypes in the offspring of a genetic cross. In this case, the F₂ generation shows a phenotypic ratio of approximately 9:3:3:1 for tall and short plants with blue and white seeds, which helps to identify the dominant and recessive traits based on their frequencies in the offspring.