A loss of smell or taste can be frustrating. But in most cases, this impairment is only temporary with a complete loss of the two important senses being rare. Smell impairment can be partial or total. A temporary loss of smell results from nasal congestion, allergic rhinitis, colds and other nasal allergies. When the nasal passage is blocked, it hinders the sense of smell and taste as these are related functions. Nasal tumors, polyps and septal deformities also prevent air flow to the region consisting of smell receptors. With age, the sense of smell can be affected to a degree.
A gene mutation is a permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people.
In biology, a mutation is a permanent change of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements. A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product. ( 2 See Stop codon .).