Final answer:
The short trait seems to disappear in the F1 generation due to dominant and recessive alleles. It is still present in the genetic makeup and can reappear in the F2 generation.
Step-by-step explanation:
In the F1 generation, the short trait seems to disappear because of dominant and recessive traits. Each individual has two copies of a gene, called alleles, for each trait. In this case, the short allele is recessive, while the tall allele is dominant.
When a heterozygous individual (one tall allele and one short allele) is crossed with another heterozygous individual, the Punnett square predicts a ratio of 3:1, with each offspring having a 25% chance of being short. However, the dominant tall allele masks the expression of the recessive short allele, making the trait seem to disappear in the F1 generation.