Proteins are the building blocks of our body; good examples include muscle and bones. Proteins also conduct the chemical reactions and signal transmissions in specific pathways in our cells. Proteins are amino acid sequences, which assemble into certain structures according to instructions provided to them by their respective coding genes. Every combination of three nucleotides in DNA (called a codon), codes for one specific amino acid. So if a protein is 100 amino acids long its gene should contain 300 nucleotides.
Proteins are where the effects of mutations are felt. If there is a mutation in an exon in DNA sequence then a wrong amino acid is incorporated in its protein structure. A wrong amino acid could change the structure of a protein such that its function is either reduced or lost. Since each protein is specialized to be part of a structure or a chemical pathway in our body then its lost function will have negative consequences and lead to diseases such as genetic disorders.