Bio Chp 11

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Bio Chp 11
2011-03-24 22:46:11
Mendelian Genetics biology

Chapter 11 of the biology textbook that goes over Mendelian genetics
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  1. Gregor Mendel
    • The father of genetics
    • -mid 19th C.
    • -pea plants

    Austrian monk & naturalist

    Wasn't truely recognized for his work until decades after his death
  2. Mendel's Main inferences
    • Basic units of genetics are material elements
    • These elements come in pairs
    • these elements (today called genes) retain their characteristics through many generations
    • these element (gene) pairs separate during gamete formation
  3. Mendel's Experimental subjects
    • capable of self-pollination

    therefore can be cross pollinated

    peas: seeds in the ovary
  4. Phenotype
    Physiological features

    Example: color, size, etc.
  5. Genotype
    Genetic makeup

    Technically codes for proteins

    (phenotype is controlled by its genotype)
  6. Alleles
    one of the alternative forms of a single gene
  7. Cross pollination
    • P generation: parent (started with "true breeding" parents)
    • F1 = first fillal generation

  8. F1 generation self-pollination..
    • 3:1 ration, yellow: green seeds
  9. Dominant
    • an allele that is expressed in the heterozygous condition
    • (uppercase lettter)

    • Example:
    • heterozygous peas (Yy) the yellow was the portion that showed.
  10. Recessive
    • An allele that is not expressed in the heterozygous condition
    • (lower case letter)

    • Example:
    • heterozygous peas (Yy) the green is the recessive because you cannot see it
  11. Three Genotypes yield Two phenotypes
  12. Chromosomes and Phenotypes
  13. Punnett Squares
    Give expected phenotypic and genotypic ratios of offspring

  14. Law of Segregation
    Differing characteristics in organisms result from two genetic elements (alleles) that separate in gamete formation

    • -Each gamete only gets one of the two alleles
    • -homologous chromosomes separate during Metaphase I of meiosis
    • -this is how Yy could never give rise to yy
  15. Law of independent assortment
    Genes for different characters are passed on independently of each other
  16. Incomplete Dominance
    • Heterozygote phenotype is intermediate beetween either of the homozygous phenotypes
    • (Mendel's rules do not apply to all intstances of inheritance)

    EXAMPLE: the cross of a RR red snapdragon with an rr white snapdragon results in a Rr pink snap dragon...why isn't this blending?

    ANSWER: beause the characteristics Rr is STILL there and can be passed down to later generations. Also there isn't enough pigment of the dominant red color to color the entire flower.
  17. Codominance
    • 2 alleles are equally dominant
    • -Each has different phenotypic effects
    • -both effects expressed in organisms heterozygous for that gene

    • EXAMPLE: blood type in humans
    • -3 different alleles: A, B, and O
    • -A and B are codominant (think blood type AB)
    • -O is recessive

    (blood type is based on the surface glycolipids..)
  18. Multiple Alleles
    When 3 or more alleles of the same gene exist in a population

    NOTE: no single person can have more than two alleles for a gene...but a population can have multiple variants

    • EXAMPLE:
    • Blood Type
  19. Polygenic Traits
    • Inheritance of a genetic character that is determined by the interaction of multiple genes
    • -each gene has a small, additive effect on trait
    • -more common than traits governed by single genes
    • -display "continuous variation"

    EXAMPLES: skin color, hair color, eye color, height. etc.
  20. Gene-Environment Interactions
    Effects of genes can vary greatly depending on environment.

    Environmental factor: any external influnce that is favorable or unfavorable for the development of a trait in an organism.

    • EXAMPLE: Hydrangeas
    • depending on the pH of the soil (acidic or basic) will determine the color of the hydrangeas
  21. Pleiotropy
    Single gene influences multiple phenotypic traits

    • EXAMPLE: Fragile X Syndrome
    • -break on X chromosome which can cause:
    • Mental retardation, abnormally long face, large ears, large testicles.