Nucleus Control:

  • cell development is controlled by the nucleus.
  • 1943 Joachim Hammerling uses algal cells to prove this.showed the nucleus does this vai chemical messengers (proteins). mrna codes for the proteins that determine the structure and function of the hats. 

Adult Cell Cloning:

  • dolly the sheep - proved that all genetic information needed for making a complete orgnaism is held in every cell. includes those with specialised functions. 

Difference In Gene Expression:

  • as embryo develops the cell differentiates - become specialised for a particular function. 
  • structure and function of each cell type depends on the proteins that it synthesis. 
  • every cell contains the genes to make every protein but each cell will ony express some of them - genes will be either switched on or off. 
  • whether genes are switched on or off depends on the starting position of the cells in the embryo and the chemical gradients it produces. 
  • some genes will produce signal proteins - these switch on other genes leading to cell specialisation. differentiation begins. the chemical differences in the cells increases so differentiation continues. 
  • Igor Dawid & Thomas Sargent - seperated double hybrid strands - found the two cell swree expressing some of the same genes and some different ones. showed that different genes are expressed in different cells. 

Gene Expression:

  • for a gene to be expressed mrna must be made/transcribed. 
  • for mrna to be made rna polymerase must be able to bind to the section of dna immediately before the gene - this section is the operator gene in prokaryotes and the promoter region in eukaryotes. 

Switching Genes…


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