lec 5 - Organization of genes is different in prokaryotes...

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Organization of genes is different in prokaryotes and eukaryotes.
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In prokaryotes, genes with a common function are often arranged linearly in operons and transcribed together on a single mRNA. There are very few non-coding gaps of DNA in prokaryotic genomes.
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Genes analogous to trpEDCBA in yeast (a eukaryote) are scattered on several chromosomes. That means that co- regulation is not achieved simply by physical linkage.
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In prokaryotes, mRNAs are directly transcribed from DNA. But in eukaryotes, transcripts must go through several processing steps before becoming mRNAs.
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RNA processing: As the 5’ end of a nascent RNA chain emerges from RNA polymerase, the 5’ cap structure (7-methyl- G) is added to it by several enzymes. The cap is linked to the 5’ terminal nucleotide of the RNA by a 5’-5’ linkage.
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RNA processing in eukaryotes involves polyadenylation (addition of 100 to 250 A residues by poly(A) polymerase, intron excision, and exon ligation.
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lec 5 - Organization of genes is different in prokaryotes...

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