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==Experiments==
A study by Cindy L. Wills and Bruce J. Dolnick from the Department of Experimental Therapeutics at the Roswell Park Memorial Institute in Buffalo, New York and from the Cell and Molecular Biology Program at University of Wisconsin in Madison, Wisconsin was made to understand cellular processes involving primary transcripts. Researchers wanted to understand whether 5-[[Fluorouracil]] (FUra), a drug known for use in cancer treatment, inhibits or shuts down [[dihydrofolate reductase]] (DHFR) pre-mRNA processing and/or nuclear mRNA stability in [[methotrexate]]-resistant KB cells. Long-term exposure to FUra had no effect on the level of DHFR pre-mRNA containing certain introns, which are sections of pre-mRNA that are usually cut out of the sequence as a part of processing. However, levels of total DHFR mRNA decreased two-fold in cells exposed to 1.0 microM FUra. There was no significant change in the [[half-life]], which refers to the time it takes 50% of the mRNA to decay, of total DHFR mRNA or pre-mRNA observed in cells exposed to FUra. And nuclear/cytoplasmic RNA labeling experiments demonstrated that the rate of nuclear DHFR RNA changing to cytoplasmic DHFR mRNA decreased in cells treated with FUra. These results provide further evidence that FUra may help in the processing of mRNA precursors and/or affect the stability of nuclear DHFR mRNA.<ref>{{cite journal | last1 = Will | first1 = CL | last2 = Dolnick | first2 = BJ | date = Dec 1989 | title = 5-Fluorouracil inhibits dihydrofolate reductase precursor mRNA processing and/or nuclear mRNA stability in methotrexate-resistant KB cells | url = | journal = J Biol Chem
Judith Lengyel and Sheldon Penman from the department of Biology at the [[Massachusetts Institute of Technology]] (MIT) in Cambridge, Massachusetts wrote an article about one type of primary transcript involved in the genes of two [[dipteran]]s, or insects that have two wings: ''[[Drosophila]]'' and ''[[Aedes]]''. The article describes how researchers looked at hnRNA, or basically pre-mRNA, primary transcripts in the two kinds of insects. The size of hnRNA transcripts and the fraction of hnRNA that is converted to mRNA in cell lines, or groups of cells derived from a single cell of whatever one is studying, of ''Drosophila melanogaster'' and ''Aedes albopictus'' were compared. Both insects are dipterans, but ''Aedes'' has a larger genome than ''Drosophila''. This means that Aedes has more DNA, which means more genes. The ''Aedes'' line make larger hnRNA than did the ''Drosophila'' line even though the two cell lines grew under similar conditions and produced mature or processed mRNA of the same size and sequence complexity. These data suggest that the size of hnRNA increases with increasing genome size, which is obviously shown by Aedes.<ref>{{cite journal | last1 = Lengyel | first1 = J | last2 = Penman | first2 = S | date = Jul 1975 | title = hnRNA size and processing as related to different DNA content in two dipterans: Drosophila and Aedes | url = | journal = Cell | volume = 5 | issue = 3| pages = 281–90 | pmid = 807333 | doi=10.1016/0092-8674(75)90103-8}}</ref>
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