Many scientists have argued that the null hypothesis should be splicing noise, putting the burden of proof on those who claim biologically relevant alternative splicing. According to those scientists, the claim of function must be accompanied by convincing evidence that multiple functional products are produced from the same gene. Biological functions and evolution
While introns do not encode protein products, they are integral to gene expression regulation. Some introns themselves encode functional RNAs through further processing after splicing to generate noncoding RNA molecules. Alternative splicing is widely used to generate multiple proteins from a single gene. Furthermore, some introns play essential roles in a wide range of gene expression regulatory functions such as nonsense-mediated decay and mRNA export.The biological origins of introns are obscure. After the initial discovery of introns in protein-coding genes of the eukaryotic nucleus, there was significant debate as to whether introns in modern-day organisms were inherited from a common ancient ancestor (termed the introns-early hypothesis), or whether they appeared in genes rather recently in the evolutionary process (termed the introns-late hypothesis). Another theory is that the spliceosome and the intron-exon structure of genes is a relic of the RNA world (the introns-first hypothesis). There is still considerable debate about the extent to which of these hypotheses is most correct. The popular consensus at the moment is that introns arose within the eukaryote lineage as selfish elements.Early studies of genomic DNA sequences from a wide range of organisms show that the intron-exon structure of homologous genes in different organisms can vary widely.
Once CBV-TP is integrated into the viral DNA, transcription and HIV reverse transcriptase is inhibited. Pharmacokinetics
Abacavir is given orally and is rapidly absorbed with a high bioavailability of 83%. Solution and tablet have comparable concentrations and bioavailability. Abacavir can be taken with or without food.Abacavir can cross the blood-brain barrier. Abacavir is metabolized primarily through the enzymes alcohol dehydrogenase and glucuronyl transferase to an inactive carboxylate and glucuronide metabolites. It has a half-life of approximately 1.5-2.0 hours. If a person has liver failure, abacavirs half life is increased by 58%.Abacavir is eliminated via excretion in the urine (83%) and feces (16%). It is unclear whether abacavir can be removed by hemodialysis or peritoneal dialysis. History
Robert Vince and Susan Daluge along with Mei Hua, a visiting scientist from China, developed the medication in the 80s.Abacavir was approved by the U.S. Food and Drug Administration (FDA) on 18 December 1998, and is thus the fifteenth approved antiretroviral drug in the United States. Its patent expired in the United States on 26 December 2009. Synthesis
References
Further reading
External links

"Abacavir". Drug Information Portal. U.S. National Library of Medicine. "Abacavir sulfate". Drug Information Portal. U.S. National Library of Medicine. Abacavir pathway on PharmGKB