lec 3

• Genes


  DNA sections that code for specific proteins or functional RNA, playing a crucial part in biological functions

  
• Alleles


  Variations of genes, leading to diverse traits such as eye color
• Mutation


  Alteration in the DNA sequence of an organism

  
• Mutant


  Organism in which a mutation has occurred
• Mutation


  1. DNA undergoes frequent chemical change, especially during replication

  2. Caused by environmental factors such as exposure to radiation or certain chemicals

  3. Most changes repaired: DNA changes are often repaired promptly

  4. Unrepaired changes lead to mutation: Failure of DNA repair results in mutation

  
• Wild type


  Appearance typical of the species in a natural population, common forms of a gene in a given species, predominant phenotype, genotype, or gene in a natural population, normal gene or allele, contrasting with mutants
• Mutations are rare events
• Natural selection


  Governs the fate of mutations over time
• Mutations offering advantages


  Are selected and may become prevalent in the population
• Deleterious mutations


  Are eliminated by natural selection
• Neutral mutations


  With neither advantage nor disadvantage, may endure in the population
• Single-base substitutions/Point mutations


  A single base, say an A, becomes replaced by another
• Missense mutations


  DNA change that results in different amino acids being encoded at a particular position in the resulting protein, some may alter the function of the resulting protein

  
• Nonsense mutations (stop mutation)

  Change in DNA that causes a protein to terminate or end its translation earlier than expected, a common form of mutation in humans and other animals that causes a shortened or nonfunctional protein to be expressed

  
• Silent mutations


  No effect, cannot be detected without sequencing the gene

  
• Frameshift mutation


  Insertion or deletion of nucleotide bases, disturbs the normal reading frame, subsequent gene sequences will be misread, can lead to the incorporation of incorrect amino acids into the protein or the generation of a codon that prematurely halts protein synthesis

  
• Germline mutations


  In gametes, significant because they can be transmitted to offspring and every cell in the offspring will have the mutation
• Somatic mutations


  Occur in other cells of the body, may have little effect on the organism because they are confined to just one cell and its daughter cells, cannot be passed on to offspring
• Deleterious mutations


  Null or knock-out mutations, result in the loss of gene function

  
• Gain-of-function mutations


  Can create new or enhanced gene product functions
• Lactase persistence


  • Variation in a genetic switch that keeps the lactase gene active, allowing people to keep milk in their diets even as adults
• Mutations in DNA repair genes


  Can weaken the cell's ability to correct other mutations, accumulation of mutations due to impaired DNA repair in somatic cells can lead to uncontrolled cell division seen in cancers

  
• Conditions caused by mutations in DNA repair genes within germ cells

  • Hemophilia - inherited bleeding disorder, mutation prevent the function of clotting protein

  
• Applications of mutations


  • Genetic Engineering
  • Medical Research
  • Evolutionary Studies
  • Biotechnology
  • Drug Development
  • Cancer Research
  • Environmental Monitoring
  • Forensic Science
  • Microbial Biotechnology
  • Animal and Plant Breeding
• Evolution


  The change in frequency of an existing gene variant in the population due to random chance, the transfer of genetic material from one population to another
• Human Evolution


  The process by which living organisms change over time through changes in the genome, these changes start from mutations - create genomic diversity - lead to individuals with modified biological functions or physical traits, the individuals best adapted to their environment tend to produce more offspring – creates successive generations of the species, this process can span millions of years, resulting in species with divergent functions, physical traits, or even the emergence of entirely new species
• Genetic variation is useful because it helps populations change over time
• Variations that help an organism survive and reproduce are passed on to the next generation, variations that hinder survival and reproduction are eliminated from the population
• The whole human family is one species with the same genes
• Mutation creates slightly different versions of the same genes, called alleles
• Small differences in DNA sequence make every individual unique, they account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease

  
• Once new alleles arise, cell division and sexual reproduction combine different alleles in new ways to increase genetic variation
• Individuals in other species vary too, in both physical appearance and behavior