Alleles are:
1. different phenotype
2. true breeding homozygotes
3. different molecular forms of a gene
4. heterozygotes

F₂ generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1: 2: 1. It represents a case of:

1. Co-dominance

2. Dihybrid crosses

3. Monohybrid crosses with complete dominance

4. Monohybrid crosses with incomplete dominance