Cellular Control

• A genome is the complete set of DNA in an organism
• a codon is 3 base pairs which code for an amino acid
• in Prokaryote cells, you have circular chromosomal DNA (nucleoid), or small loops of plasmid DNA rings.
• Eukaryotic cells are a diploid set of chromosomes, with mitochondrial DNA and chloroplast DNA.
• The non-coding regions of DNA are:

  • Intergenetic regions
  • Introns
• A point mutation is a change of a single base in DNA sequencing
• Point mutations can occur during DNA replication
• Types of mutagens are:

  • Chemical
  • Physical
  • Biological
• The 4 outcomes of a point mutation is:

  • no change in phenotype
  • Deletarious mutations
  • Advantageous mutations
  • Neutral mutations
• A no change in phenotype as a result of point mutations is also called a silent mutation. They do not affect the stucture, and therefore structure of a protein because they occur in the non-coding regions of DNA. They may occur within the coding region of an amino acid, but since DNA is degenerate, there is no change. It could also occur in the coding region and change the amino acid sequence, but it doesnt affect the foling of the tertiary structure.
• A deleterious mutation is a mutation which changes the phenotype of the organism. This occurs when the majority of mutations are lethal or disadvantageous to the organism.
• Advantageous mutations change the phenotype of an organism in a way that is beneficial to the organism and will be selected for in natural selection
• A neutral mutation is a change in phenotype but theres no advantage or disadvantage, it is just neutral.
• A point mutation is brought about by base substitution, base deletation, base insertion/addition
• base substitution allows for :

  • Silent mutations (amino acid sequence is unaltered)
  • Missense mutations (One amino acid is incorrectly coded for)
  • Nonsense mutations (codon changes to stop codon & polypeptide chain is terminated)
  • Frameshift mutatioins (caused by an addition/detetion of a base, leading the entire gene following the mutation to be read incorrectly, UNLESS 3 bases are added/deleted)
• chromosome mutations iccur due to mistakes in the crossing over in Prophase I of meiosis and mitosis
• Non-disjunction is where a pair of homologous chromosomes do not divide. This can be VIA deletion, addition, inversion, or translocation.
• The levels of control of gene expressions:

  • Transcriptional level
  • post-transcriptional control
  • Translocational control
  • Post-translocational control