cell differentiation and gene expression

• what is a genome?

  the entire set of DNA in a cell including all the genes
• • stem cells contain the same genes but not all are expressed
  • under specific conditions genes are activated or inactivated
  • mRNA is only transcribed from active genes
  • the mRNA is then translated into proteins
  • these proteins modify the cell to determine it’s structure and control processes
  • these changes caused by proteins cause the cell to become specialised
  • these changes are hard to reverse so once a cell is specialized it stays specialised
• what is an operon?

  • a section of DNA that contains a cluster of structural genes that are transcribed together as well as control elements
• what do structural genes do?


  they code for useful proteins such as enzymes
• what are control elements?

  • they include promoters (dna sequence located before the structural genes that RNA polymerase binds to)
  • include operators (a sequence that transcription factors bind to)
• What is a regulatory gene?

  an activator or a repressor