Gene Function Analysis in Eucaryotes 2

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  • Gene Function Analysis in Eucaryotes 2
    • Mendel 2nd law
      • Proved by presence of non parental matches in crosses
      • Mendel didn't notice many genes have more then 1 allele. Many alleles have codominanceor incomplete dominance. Many genes exhibit genetic lineage
        • Incomplete dominance; phenotype is an intermediate
        • Co-dominance; more than 2 alleles for a characteristice.g ABO blood system
          • You can be O (no surface angtigen A), B (with surface antigen B) or AB (with both)
        • Genetic linkage; Thomas Morgan carried out experiment with drosophila
          • Created f1 generation which were grey with normal wings  (dominant characteristics). When bread with black fly with vestigial wings expected 4 phenotypes
            • Outcome; only parental phenotypes occurred. However on larger scale, these other non-parental genes were created.
              • Concluded these genes located on same chromosome and meant the rare outliers were due to chromosome cross over (genetic recombination)
                • Also data suggests number of recombinantsproportional to physical distance between linked genes
    • Modern Application of Classical genetic analysis
      • Dissecting biological mechanisms
      • Seeing a symptom and finding the gene causing it
      • Induced genetic variation via chemicals or radiation
      • Engineering; removing (targetted mutations), adding (transgress)
      • Genetic Screening
        • Identifies mutations; most have recessive phenotypes
        • Forward genetics
          • Seen in fruit flies which have certain genes not expressed causing body parts not to develop e.g. pair gene switched off causes all even segments to not be present. Gap gene causes only head and tail present. Segment polarity gene causes only anterior parts present.
        • Reverse Genetics; gene addition, replacement or knockout to see effects
      • Complementation testing
        • Can tell us whether two independently isolated mutations with similar phenotypes lie in the same or different gene
          • If in same gene wild type does not occur. If in different genes, wild type is restored as mutations complement each other


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