Th2L01 Prokaryotic vs. eukaryotic genes

Th2L01 Prokaryotic vs. eukaryotic genes

1. Eukaryotic genes

   • Exons
     • Genome expressed sequence of DNA Genome expressed sequence of DNA
     • Codes for a protein
     • About 1.5% of DNA
     • Found in mature mRNA
   • Introns
     • Non-coding
     • Interrupt mRNA
     • 23% of DNA
     • Not found in mRNA
   • Non-coding DNA
     • Untranscribed regions near genes
       • ca. 2% of non-coding regions of DNA
       • Areas flanking genes, esp. at the 5' end are important regulatory elements that control the production of mRNA
     • Repetitive DNA
       • Nucleotide sequences, usually noncoding, that are present in many copies in a eukaryotic genome
       • The repeated units may be short and arranged tandemly (in series) or long and dispersed in the genome
       • about 50% of DNA
       • Main types
         • Retrotransposable elements
           • Characteristics
             • moderately repetitive
             • thought to move to randomly selected new locations
               • method of movement unknown in human genome
             • classified according to origin
               • LINES
                 • Viral retrotransposable elements
                 • Long Interspersed Elements
                 • appears to contains its own reverse transcriptase
               • SINES
                 • Non-viral retrotransposable elements
                 • Short Interspersed Elements
         • Satellite DNA
           • short sequences of DNA that are tandemly repeated as many as 10 million times in the DNA
           • much of it is located in the telomeres
           • 8% of entire genome
           • Role
             • structural properties of DNA
           • Clinical sig.
             • Provides genetic fingerprint □ Used in paternity testing and forensic science
     • Uncharacterised/junk DNA
       • about 25% of DNA

2. Prokaryotic genes

   • Promoter - coding sequence (5' to 3')
   • Transcriptor terminator
   • Transcribed into mRNA
     • mRNA translated by ribosomes to give a polypeptide

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