Patterns of Inheritance Complete Dominance Incomplete Dominance Co-dominance Co-dominance with...

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  • Patterns of InheritanceComplete DominanceIncomplete DominanceCo-dominanceCo-dominance with Multiple AllelesSex Linked

  • Impact of Mendels WorkMendel published his results in 1866Paper received little noticeMendel discontinued his experiments in 1871Paper rediscovered in 1900

  • Mendels Law of Segregation

    An individual inherits ONE unit of information (allele) about a trait from each parent

    During gamete formation, the alleles separate from each other (Tt T or t )

    page

  • Mendels Law of Independent AssortmentMendel concluded that one gene did not affect another gene

    Alleles for these genes separated random from each otherTtRr T or t R or r so TR Tr tR tr

    page

  • Complete Dominance Inheritance

    2 alleles; one dominant or the other

    if dominant allele present, it will be expressed

    2 distinct phenotypes; 3:1 ratio

  • Genetics After Mendel1. Incomplete Dominance2. Co-dominance3. Co-dominance with Multiple Alleles4. Sex Linked

  • Incomplete DominanceXHomozygous parentHomozygous parentAll F1 are heterozygousXF2 shows three phenotypes in 1 : 2 : 1 ratio1. Incomplete Dominanceneither allele is completely dominant over the other

    3 phenotypes

    heterozygous is a intermediate or blendpage R Rr r R rR rR rR RR rr rR r

  • both alleles are expressed at the same time in the heterozygous (roan)

    3 phenotypes;1 : 2 : 1 ratio

    page

    2.Co-dominance

  • 3. Co-dominance with Multiple Alleles:ABO Blood types3 alleles; two that are co-dominant and one recessiveIA , IB , i page

    GenotypePhenotypeIAIA or IAiType AIBIB or IBiType BIAIBType ABiiType O

  • ABO Blood Typestype of blood determined by antigen on surface (flag)type of blood make antibodies against other antigens

  • Blood TransfusionsDuring transfusions recipients antibodies in plasma will attack blood cells that have an unfamiliar surface antigen (agglutination clumping of blood)

    Type AB is universal recipient since it does not have any antibodies because it has both antigens any blood can be donated to them!Type O is universal donor since it has neither type A nor type B antigen for antibodies to attack give to anyone

  • Transfusions

    Antibodies Can Receive Blood FromType A B A or OType B A B or OType AB none A, B, AB, OType O A and B only O

  • Rh Factoranother protein marker on red blood cellsindependent of type of bloodinheritance works according to complete dominanceeither Rh+ or Rh- ; Rh+ is dominant special problem during pregnancy of second child if mom is Rh- and first was baby Rh+

  • 4. Sex Linkedgenes on the sex chromosomes

    have different probabilities in females and males

    examples of recessive X linked traits hemophilia

    red/green colour blindness page

  • Other types of Inheritance5. Multifactorial/Multiple Genes/Polygenic

    6. Sex Limited

    7. Sex Influenced

    8. Gene Linkage

  • 5. Multifactorial/Multiple Genes/Polygenic

    Traits show wide range of phenotypic expression; continuous distribution Controlled by more than one gene

    Traits maybe influenced by other factors

    Examples human hair colour, height, eye colour, skin colour

  • Describing Continuous Distribution

  • 6. Sex Limited TraitsExpression of the trait is limited by sex of the individualTraits NOT on sex chromosomeThought to be influenced by hormonesExample: heavy beards phenotype in males only but females inherit but dont express it but can pass trait to sons

  • 7. Sex Influenced TraitsIdea of how genes are influenced by internal environments

    Genes may be dominant in one sex but recessive in other; genotype interpreted differently

    Baldness dominant trait in males; in females recessive trait and dont see bald but rather thin

  • Nature verse NurtureExpression of traits are not fully under control of just what your genotype is (NATURE)

    An organisms internal environment and external environmental factors influence how genes may be expressed (NURTURE)

    Example height may have genetics to be tall but if there is hormonal imbalance or nutritional deficiency than wont reach genetic potential

  • Temperature Effects on Phenotype Rabbit is homozygous for an allele that specifies a heat-sensitive version of an enzyme in melanin-producing pathway

    Melanin is produced in cooler areas of body

  • Environmental Effects on Plant PhenotypeHydrangea macrophylla

    Action of gene responsible for floral color is influenced by soil acidity

    Flower color ranges from pink to blue