Explain why pedigree are needed to identify the carriers of a recessive trait in a family?

I have two answers for you. A simple one and a much longer one lol: 
1. Carriers silently carry a copy of the recessive gene. They can only be identified if they have a child who shows the disease.

2. A pedigree displays the hereditary outcome of a certain species that has not crossbred with another type e.g. dogs--> a pedigree poodle is the offspring of 2 poodles and there has never been any other type of dog crossbred in the earlier generation of that poodle so it's a pure breed. There are dominant and recessive traits that pass down from generation to generation and they can be seen in the offspring. The dominant gene shows up a lot more. For example, if you had two purebred poodles and they were both white but when they had babies, 3 of them were white but one of them was brown, the white colour would be the Dominant colour and the brown would be recessive colour. If one of the poodle parents was another breed of dog, then we wouldn't be able to tell if the brown poodle was brown due to a recessive trait from the purebred poodle parent or if it was inherited from the other breed parent. 

Six amino acids have side chains that are polar but not charged. these are serine (ser), threonine (thr), cysteine (cys), asparagine (asn), glutamine (gln), and tyrosine (tyr). these amino acids are usually found at the surface of proteins, as discussed in the proteins 2 module.