The recessive trait phenotype disappears in a one-trait test cross in the F1 generation. This phenotype can reappear in the F2 generation.
A dominant genetic trait appears in every generation of offspring because only one copy of the dominant allele is needed for the trait to be expressed.
Mendel's Law - The first law of Mendel states that "In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype."
All offspring would have the phenotype of having a green color (G) due to the dominant trait, but a varying phenotype for the second trait as half the offspring would have a smooth texture (bb) and the other half would have a wrinkled texture (Bb).
The outward appearance is called the phenotype
Phenotype
A dominant genetic trait appears in every generation of offspring because only one copy of the dominant allele is needed for the trait to be expressed.
A trait in the f1 generation that is different than that of the parental phenotype is known as a hybrid. This occurs as a result of two distinctly different parents producing a phenotype that is uniform and new.
Mendel's Law - The first law of Mendel states that "In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype."
The phenotypes present in the F1 generation depend on the phenotypes of the parental generation (and the environment). The F1 generation will display the dominant trait(s). For example, if T is tall and t is short, in the cross TT X tt the F1 generation will have the phenotype corresponding to the T allele (tall).
The second Mendelian Law is the Law of Segregation. It states that in a cross the parental traits do not merge in the first offspring generation (ie. the recessive, "weaker" trait does not disappear for good) but instead appear unchanged in the second offspring generation. For example, if you cross homozygous dwarf pea plants to homozygous tall, all members of the first offspring generation will be tall. This makes it seem as if the dwarf trait disappears, but it does not. If you inbreed the first offspring generation, you get 25% dwarf plants in the second offspring generation. So the "lost" trait reappears.
To determine the genotype of an individual that shows the dominant phenotype you would cross that individual with one that is homozygous recessive. A monohybrid cross of two individuals that are heterozygous for a trait exhibiting complete dominance would probably result in a phenotype ratio is 3 dominant 1 recessive.
No genes disappear in the F1 generation. Each of the F1 plants was heterozygous, having both a dominant and recessive alleles. The recessive phenotype disappears in the F1 generation because all members of that generation carry a dominant allele. In the F2 generation, the recessive phenotype will reappear.
Test Cross
The ratio of dominant to recessive phenotype in the F2 generation of Mendel's experiment was 3:1. This means that for every 3 individuals expressing the dominant trait, there was 1 individual expressing the recessive trait.
The expected phenotype ratio of seed color in the offspring of an F1 x F1 cross is 3:1. This is because the F1 generation is heterozygous for the trait, resulting in a 3:1 ratio of dominant to recessive phenotypes in the offspring.
In a monohybrid cross of tall dominant and dwarf recessive plants, all the F1 plants will be tall. This is because the tall trait is dominant over the dwarf trait, so the presence of one dominant allele is sufficient to exhibit the tall phenotype. The dwarf trait will be masked in the F1 generation.
when observing the F1 generation of a monohybrid cross