DNA Transcription

• DNA is a double helix
• our familiar sequence,
  the DNA code for the 'protein' Met-Gly-Ser-Glu-Val-STOP
  was:
  • 3'-TACCCGAGCCTCCAGATT-5'
• as a double strand becomes:
  • 3'-TACCCGAGCCTCCAGATT-5' = template strand (sense)
  • 5'-ATGGGCTCGGAGGTCTAA-3' = coding strand (antisense)
• the entire gene is 20 - 200 base pairs longer than this
  • the extra base pairs are a promoter
  • the promoter is involved in initiating transcription
  • may (?) include
    • a file-name identifying the gene,
    • and a file-length of gene
• in eukaryotes, there is also associated chromatin protein sheath
  • there are side chain 'markers' on chromatin near end of gene
  • may (?) serve as address markers for start of gene
• the nuclear region has numerous small RNA's probably involved in
  • regulation of transcription
  • and in mediating stimulus-response

process of transcription

tentative explanation of the process

• small RNA's & associated proteins attach to promoter
• unwind the double helix for the length of gene
• assemble mRNA along template strand
• rewind the double helix
• mRNA may be 'edited' to final mRNA form
• final mRNA sent to e.r. for transport to ribosomes for translation

A major question yet to be resolved is how the nucleus converts information about the environment [or a stimulus, internal to and/or external to the cell] into a decision about which genes to activate, ultimately producing the proteins needed to respond to the environmental stimulus.

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© 2004-2005 TwoOldGuys ™

revised 19 aug 2006