Chpt. 11.2 complex inheritance leftovers
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Chpt. 11.2 complex inheritance leftovers

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    Chpt. 11.2 complex inheritance leftovers Chpt. 11.2 complex inheritance leftovers Presentation Transcript

    • Complex Patterns of Inheritance
    • Sickle-cell anemia
      • Autosomal recessive trait
      • 1 in 12 African Americans (black Americans whose families originated in Africa) is heterozygous (carrier)
      • Common in white Americans whose families originated in the countries surrounding the Mediterranean Sea
      • Person suffers from anemia (low # rbc)
      • Abnormally shaped cells slow blood flow, block small vessels, and results in tissue damage and pain
      • Have other serious health problems because of the impaired circulation
      • Treatments – blood transfusion and drug therapy
    •  
    • Sex Determination
      • Sex chromosomes determine an individual’s gender.
      • Humans have 23 pair (46 total) of chromosomes in each of somatic cells
      • 22 are autosomes
      • The 23rd pair are sex chromosomes
        • XX = female
        • XY = male
    • Dosage Compensation
      • The X chromosome carries a variety of genes that are necessary for the development of both females and males.
      • The Y chromosome mainly has genes that relate to the development of male characteristics.
    • Chromosome Inactivation
      • Chromosome Inactivation- random inactivation of the X chromosome.
      • Example – calico cat
      • One X chromosome codes for orange fur and one X chromosome codes for black fur.
    • Sex linked traits
      • Sex-linked traits (X-linked)- traits controlled by genes located on the X chromosome.
      • X-linked inheritance - passed on by the female – even if recessive, the trait is expressed because the male does not pass an X for a dominant allele.
      • Ex: Color blindness and hemophilia
    •  
    • Muscular dystrophy is a deadly disorder in which the muscles grow progressively weaker. The disease is caused by a recessive gene on the X chromosome
    • Polygenic Inheritance
      • Polygenic Inheritance- pattern of a trait that is controlled by two or more genes
      • Genes may be on the same chromosome or different chromosome
      • All heterozygotes are intermediate in phenotype
    • Polygenic Inheritance
      • Inheritance pattern of a trait that is controlled by two or more genes
      • Skin color, eye color
      • Will express a range of colors (intermediate)
    • Environmental Influences
      • The environment also has an effect on phenotype. As organisms develop many factors influence how genes will be expressed
      • 2 environmental influences
      • Internal environment- Male and females express traits differently due to hormones
      • -Horn size in rams, feather color in peacocks
      • -Age affects how genes function
      • External environment- Temperature, nutrition, light, chemicals, and infectious agents