The pop up question at the end of this level asks why examining dna is better than considering physical traits, when do you have to rely on physical traits instead of dna

Question 1: Why examining dna is better?

Examining DNA has a greater interest than examining physical traits because it can determine the genotype of the individual and what are the two alleles that he possesses while examining its physical traits only gives us the phenotype of the individual, which has a lower value than the genotype.

Question 2:

DNA testing is more expensive than examining physical traits, so that in most cases physical features are used to study trait transmission.

There is one case where the determination of the physical trait is sufficient to determine the genotype of the individual: this is when studying codominant alleles such as ABO grouping.