Please enable JavaScript.

Coggle requires JavaScript to display documents.

Cellular Control - Coggle Diagram

- - - - (Pre-) transcriptional regulation - genes made inaccessible.
      - Transcriptional regulation - genes turned on or off.
      - Post-transcriptional regulation - mRNA modified.
      - Translational regulation - translation stopped or started.
      - Post-translational regulation - protein modification.
- - - - The situation is similar in humans where Hox A11 and Hox D11 switch on the genes for development of the forelimb.
      - It has been suggested that thalidomide may have switched off the homeobox genes for limb development.
      - This caused the birth defects typical of thalidomide use.
      - Thalidomide can certainly insert itself into DNA and inhibits production of new blood vessels in limb buds.
  - - - Proteins that affect the rate of transcription.
    - - Highly conserved genes responsible for the development of body plans.
    - - Highly conserved genes responsible for the development of body plans
    - - The part of the homeobox gene that codes for the homeodomain.
    - - Highly conserved sequence of amino acids found in all homeobox proteins; it binds to DNA to regulate transcription of developmental genes.
    - - Genes that control the growth and development of an organism.
- - - - The DNA is too large to exit the nuclear pore.
      - The double helix untwists, revealing a coding and a template strand
      - The enzyme helicase breaks the hydrogen bonds between complementary bases which ‘unzips’ the DNA.
      - Complementary bases are exposed.
      - Activated free nucleotides pair up with the exposed template strand.
      - RNA polymerase forms phosphodiester bonds between adjacent nucleotides to seal the backbone (working 3’ to 5’), allowing hydrogen bonds to form between complementary bases.
      - This continues until an exact replica is formed. mRNA then exits the nucleus by the nuclear pore and the DNA helix reforms.
    - - mRNA enters the groove between the two subunits of a ribosome.
      - The ribosome is large enough for two mRNA codons to be side by side.
      - A tRNA molecule with an anticodon complementary to the mRNA codon lines up with the mRNA strand
      - Hydrogen bonds form between the mRNA strand and the anticodon of the tRNA
      - A second tRNA bonds to the next codon on the mRNA. rRNA catalyses the formation of a peptide bond between the two neighbouring amino acids.
      - The ribosome moves along one codon at a time along the mRNA molecule, to allow the next tRNA to bind until it reaches the stop codon
  - - - A random change in the sequence of, or arrangement of, the genetic material in a cell.
    - - A random change to parts of, or whole, chromosomes.
    - - A random change to genes due to changes in nucleotide base sequences
  - - - No effect on the phenotype.
    - - Truncated polypeptide as a stop codon is formed.
    - - A different polypeptide is formed.
  - - - As a normal functioning protein is synthesised. This may be due to coding for the SAME amino acid, or for an amino acid with an R group with similar properties.
    - - Due to a change of the primary structure, the normal functioning of the protein is affected eg cystic fibrosis; non-functioning ion channel, sickle cell anaemia, Huntington’s disease
    - - Due to a change in the primary structure, the normal functioning of the protein is affected in a beneficial way eg changes to a human plasma membrane protein that prevents binding of the HIV virus and subsequent infection.
  - - - A section of one chromosome breaks off and joins another non-homologous chromosome.
    - - A section of a chromosome breaks off, is reversed, and then joins back on the same chromosome.
- - - - Programmed cell- meditated death that occurs after a multiple (50) mitotic divisions; “cell suicide”
      - Process
        
        Enzymes break down cell cytoskeleton
        
        Cytoplasm becomes dense, with organelles tightly packed
        
        Chromatin condenses and nuclear envelope breaks.
        
        DNA and organelles breaks down
        
        Blebs form in cell membrane
        
        Cell breaks into vesicles which are phagocytosed
      - Why does this process need to occur?
        
        Allows digits to form (removing ‘webbing’).
        
        Removes ineffective or harmful T lymphocytes as the immune system develops.
        
        Tadpoles lose their tails by apoptosis when they turn into frogs.
        
        Occurs when cells get too old (ageing).
    - - Traumatic cell death due to invasion or damage from pathogens which releases hydrolytic enzymes; “cell murder”