List two differences between dominant traits and recessive traits. What percentage of pea plants in the $\mathrm{F}_2$ generation were with yellow seeds in Mendel's cross between the pea plants having yellow (YY) and green coloured (yy) seeds?

According to Mendelian inheritance, traits are controlled by pairs of alleles (factors). A dominant allele (like $Y$ for yellow color) masks the expression of a recessive allele (like $y$ for green color) in a heterozygous individual ($Yy$). Thus, the $\mathrm{F}_1$ generation shows only the dominant phenotype (yellow). When these $\mathrm{F}_1$ plants self-pollinate, the recessive trait reappears in the $\mathrm{F}_2$ generation in a $3:1$ phenotypic ratio (dominant to recessive). This demonstrates that the alleles segregate during gamete formation and recombine randomly, resulting in $75\%$ of the offspring displaying the dominant yellow phenotype and $25\%$ displaying the recessive green phenotype.