Heartworms are spread to dogs through mosquito bites. Up to 14 inches long, a heartworm lives in the heart and the arteries that carry blood from the heart to the lungs. Heartworms affect how the heart functions and how blood clots and is likely to cause death if untreated. Monthly heartworm preventives are effective.
missense mutation. A substitution of a single DNA nucleotide for another. This results in the transcription of a different amino acid than is normally found in the protein coded by the gene. Missense mutations are found in diseases such as sickle cell anemia.
1 Missense mutations or nonsynonymous mutations are types of point mutations where a single nucleotide is changed to cause substitution of a different amino acid. 2  This in turn can render the resulting protein nonfunctional.utations in the structure of genes can be classified as: , 1  such as those affecting a small gene in one or a few nucleotides, including: 2  Point mutations, often caused by chemicals or malfunction of DNA replication, exchange a single nucleotide for another. 3  These changes are classified as transitions or transversions.