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8s rrnas are encoded by a larger gene 5s rrna is

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Unformatted text preview: structure and processing Eukaryotic cells have two types of rRNA genes The 18S, 28S, and 5.8S rRNAs are encoded by a larger gene 5S rRNA is encoded by a small gene Bacterial cells have a single type of gene, which encodes all three types of rRNA rRNAs are processed in both bacteria and eukaryotes: a larger RNA precursor is cleaved, trimmed, and modified to produce the rRNA species encoded by that gene rRNA gene structure and processing The numbers of rRNA genes vary from species to species In bacteria, they are dispersed; in eukaryotes, they are found in large tandem arrays (clusters) Each copy of an individual rRNA gene is nearly identical within a species What does this indicate about rRNAs? Small RNA molecules Many small RNA molecules have cellular functions, and this has been used as evidence that the first life was RNA-based (proteins came later). Examples (RNAi we will come back to later): RNA interference (RNAi) MicroRNAs (miRNAs) RNA interference Andrew Fire and Craig Mello were using antisense RNA to inhibit gene expression antisense RNA = using a single-stranded RNA complimentary to the mRNA of a gene to inhibit the expression of that gene theory: base-pairing of the message would prevent translation Weird...
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