16. What could be some weaknesses with using a test cross to determine Fred's genotype?

Weaknesses of a test cross

Explanation:

In a test cross, the homozygous recessive genes for a trait are crossed with those the individual with an unknown genotype. The homozygous alleles are the same. The unknown individual is thus, dominant, and may be either heterozygous (different alleles) or homozygous.

In sexual reproduction, gametes are formed from the independent assortment of genes. The parental genes are packaged together in new combinations. Thus, to determine an unknown, the test crosses determine which is the parent genotype through its ratios:

However, the phenotypes must be observed to give results of this cross.

wheres the answers ?

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)