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.
Gene mutations have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. Missense mutation (illustration) This type of mutation is a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene.