Explain how a change in the sequence of nucleotides in a strand of dna might cause a protein to malfunction.

Proteins are made using DNA as a template. The DNA is turned into RNA, and the RNA is then turned into DNA. 

The sequence of nucleotides is like the letters in a recipe book. They say what protein is made. So, a change in the nucleotides makes a change in the protein. Sometimes that does nothing; sometimes it causes a malfunction. It just depends on how important that section of the protein is. 

A change in these nucleotides could end up making some part of the protein different. A single nucleotide change could be silent (no change in the protein) or could change a single amino acid (amino acids are the building blocks of proteins). If that was an important amino acid, the protein might not function at all! A silent change can occur because the same set of nucleotides sometimes makes the same final amino acid (for example, reading "gcc" "gca" "gcg" or "gct" nucleotides all mean "alanine" amino acid). 

The deletion of a single nucleotide, or the addition of one, can change the entire sequence of amino acids that come after it! Nucleotides are read in sets of three, so this throws off how the DNA is read. If would be like turning "The brown fox jumps over the dog" into "The gbrow nfo xjump sove rth edo g". Completely different! All of the words are thrown off.