Answer:
Punnett squares do not provide accurate predictions on the distribution of phenotypes in offspring. ... This makes it difficult to make predictions regarding Down's syndrome since it cannot predict the prevalence of the offspring's genotypes about a population.
Step-by-step explanation:
Limitations of Punnett squares as models of inheritance include the lack of information about likely variation in small samples such as individual families and the lack of information about population prevalence of parental genotypes (so no predictions can be made about population prevalence of offspring genotypes.