The most frequent mutations due to inaccurate synthesis past CPDs are cytosine to thymine (C>T) or CC>TT transition mutations. These are commonly referred to as UV fingerprint mutations, as they are the most specific mutation caused by UV, being frequently found in sun-exposed skin, but rarely found in internal organs. Errors in DNA repair of UV photoproducts, or inaccurate synthesis past these photoproducts, can also lead to deletions, insertions, and chromosomal translocations. The entire genomes of 25 melanomas were sequenced. On average, about 80,000 mutated bases (mostly C>T transitions) and about 100 structural rearrangements were found per melanoma genome. This is much higher than the roughly 70 mutations across generations (parent to child). Among the 25 melanomas, about 6,000 protein-coding genes had missense, nonsense, or splice site mutations. The transcriptomes of over 100 melanomas has also been sequenced and analyzed. Almost 70% of all human protein-coding genes are expressed in melanoma. Most of these genes are also expressed in other normal and cancer tissues, with some 200 genes showing a more specific expression pattern in melanoma compared to other forms of cancer. Examples of melanoma specific genes are tyrosinase, MLANA, and PMEL.UV radiation causes damage to the DNA of cells, typically thymine dimerization, which when unrepaired can create mutations in the cells genes. This strong mutagenic factor makes cutaneous melanoma the tumor type with the highest number of mutations. When the cell divides, these mutations are propagated to new generations of cells.
Then, an intermediate host (the larval stage of a flea or chewing louse) will ingest an egg, which develops into a cysticercoid larva. The cysticercoid larva remains viable, but is not infective to carnivores until the flea hatches to an adult and begins feeding on a host (e.g. a dog). Approximately 36 hours after the flea has consumed a blood meal, the infective metacestode develops inside the flea. The metacestode larva must be ingested in a flea by the dog or cat during grooming in order to develop. Humans can also become infected by D. caninum by accidentally ingesting an infected flea. In the small intestine of the definitive host, the metacestode develops into an adult tapeworm, which reaches maturity 4-6 weeks after ingestion. This adult tapeworm produces proglottids, and over time, the proglottids mature and become gravid and eventually detach from the tapeworm and the life cycle starts all over again. Geographic Distribution
This parasite occurs worldwide in animals, such as dogs and cats, as well as in humans, though to a significantly lesser degree. It is the most common tapeworm of dogs and is relatively common in cats. Despite human diplydiasis being rare, instances have been reported from every inhabited continent.Human instances of diplydiasis are reported globally, and unsurprisingly roughly one third of the cases occur in children less than 6 months of age. The most at-risk age group is those that range from 2 months to 4 years old.