Chapter 9+12 Notes
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Chapter 9+12 Notes Chapter 9+12 Notes Presentation Transcript

  • Chapter 9+12 Fundamentals of Genetics And Human Genetics
  • Gregor Mendel
    • Austrian monk that studied heredity.
    • Heredity is the transmission of characteristics from parents to offspring
    • Experimented with pea plants in the garden to determine what traits were passed along.
    • He discovered the basic rules of genetics.
  • Pea Plants
    • Mendel studied 7 traits.
    • They were easily observable: plant height, flower position, pod color, pod appearance, seed texture, seed color and flower color.
    • Mendel used cross pollination in his studies to make sure each parent was the correct one he wanted.
  • Important Vocabulary
    • Pure- being a purebreed, parent always passes on one trait to the offspring
    • P 1 generation-parent or first generation
    • F 1 -filial generation or kids of the parent generation
    • F 2 - grandkids of the parent generation
  • Important Vocabulary
    • Dominant- a trait that always shows up in the F 1 generation, it is the strongest trait and will mask other traits
    • Recessive- a trait that is weaker, usually doesn’t appear in F 1 generation but appears in F 2 generation
    • Mendel discovered that certain traits were dominant and certain ones were recessive.
    • Look in your book for the list of traits.
  • Mendel’s Laws
    • The Law of Segregation states that paired factors separate during the formation of gametes (meiosis)
    • Each gamete only receives one factor or trait from each parent.
    • The Law of Independent Assortment sates that factors for different traits distribute to gametes independently regardless of the other trait.
  • Important Vocabulary
    • An allele is the factor or gene that is passed only; it is a type of gene.
    • There may be several alleles for one gene.
    • Dominant alleles have capital letters and recessive alleles have lowercase letters.
    • Genotype is the actual genetic makeup of the organism or what the genes say.
    • Phenotype is the physical look of the organism like color or texture.
    • You can see the phenotype but not the genotype.
  • YY yy fertilization ? Y Y y y Yy Yy Yy Yy What is the phenotype of the offspring? The phenotype is yellow seed color.
  • Important Vocabulary
    • Homozygous means the organism has two of same alleles for a trait.
    • Heterozygous means the organism has two different alleles for a trait.
    • Heterozygous would automatically have one dominant allele and one recessive allele.
    • Homozygous could have two dominant alleles or two recessive alleles.
  • AA aa Aa homozygous heterozygous
  • Incomplete Dominance (intermediate)
    • When two or more alleles influence the phenotype, both are expressed so neither is completely dominant or recessive.
    • This results in a third phenotype in addition to the originals.
    • The heterozygous genotype is always the new phenotype.
  • Codominance
    • This results when two or more alleles are equally dominant and both alleles are expressed in heterozygous organisms
    • Both alleles are expressed equally.
    • This is different than incomplete dominance because it isn’t a blended phenotype, is both expressed.
    • Human blood type is an example.
  • Sex Linked Inheritance
    • Some genes are found only on the X-chromosome.
    • Many disease are X-linked diseases and are more common in males than in females.
    • Males need only one copy of the bad gene while females need two copies of the bad gene.
    • Hemophilia, colorblindness and Duchenne muscular dystrophy are human diseases associated with this inheritance.
    • A carrier is heterozygous for a disease but does not have the disease. It can be passed on to their children though.
    • Sex-influences traits like baldness are influenced by the sex of the person and are expressed differently even if the gene is the same.
  • Important Vocabulary
    • Polygenic traits are controlled by more than one gene.
    • Skin color is controlled by at lease six genes which result is a different amount of pigment produced.
    • Eye color is also polygenic as well as height although environment plays a part in that as well.
  • Mutations
    • Down syndrome results when the chromosomes don’t split evenly during meiosis resulting in three chromosomes under number 21.
    • Turner’s syndrome also occurs this way and results in one less sex chromosome.
    • Disorders can also be inherited recessively or dominantly or even as a result of chromosome pieces breaking off or “jumping” around.
  • A carrier is heterozygous for a disease but does not have the disease.
  • Why would it be advantageous to be heterozygous for sickle cell trait when sickle cell is so dangerous? 1 in 500 African Americans have sickle cell anemia. 1 in 12 carry the sickle cell gene.