Question

When analyzing a pedigree, how can you determine if an individual is a carrier (heterozygous) for the trait being studied?

Answer 1

If both parents are not showing the trait while one of the children is showing it, then the parents must be heterozygous for it.

Explanation:

Drawing a pedigree starts from top to bottom, while reading it goes the other way round.
When reading a pedigree you should start from the bottom line where you have the last generation. Check the info given about the trait (if any is provided ) before doing this step, as it will help you determining the genotype.
From the phenotype of the last generation determine the genotype or all the possible gnotypes of each individual. From this information determine the alleles of the upper generation. Do the same for the previous generation.
In some cases you cannot tell for sure if the individual is homozygous or heterozygous for a specific trait unless you have a clue for that.