Question

why did the f1 offspring of mendels classic pea cross always look like one of the two parental varieties?
one allele was dominant.
no genes interacted to produce the parental phenotype.
the traits blended together during fertilization.
each allele affected phenotypic expression.

Explanation:

Mendel's experiments showed that when there is a dominant - recessive relationship between alleles (as per his law of dominance), the dominant allele masks the expression of the recessive allele. In the F1 generation of his classic pea cross (e.g., cross between pure - breeding tall and short pea plants), the F1 offspring showed the phenotype of the dominant allele (tall in this case).

• The statement "No genes interacted to produce the parental phenotype" is incorrect. Gene interactions (in the form of allele - allele interactions) are crucial in determining phenotypes.
• "The traits blended together during fertilization" is against Mendel's findings. Mendel's work disproved the blending theory of inheritance.
• "Each allele affected phenotypic expression" is not in line with the law of dominance. In a simple dominant - recessive relationship, only the dominant allele affects the phenotypic expression in the heterozygous state (F1 generation is heterozygous in Mendel's monohybrid cross).

Answer:

One allele was dominant.