Chpt. 11.2 complex inheritance leftovers

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  • 1. Complex Patterns of Inheritance
  • 2. 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
  • 3.
    • 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
  • 4.  
  • 5. 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
  • 6. 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.
  • 7. 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.
  • 8. 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
  • 9.  
  • 10. 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
  • 11. 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
  • 12. 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)
  • 13. 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