Bio 1.10.11

  1. Why did Mendel use pea plants? (5)
    • -Easy to grow
    • -Short life span
    • -Produce many offspring
    • -Have traits that are observable and easy to identify
    • -Can control breeding
  2. Character?
    heritable feature
  3. What traits did Mendel observe?
    • -Length of stem
    • -Seed form (round)
    • -color of seed (yellow/green)
    • -Color of coat whit/gray
    • -color of seed pods (green/yellow)
    • -Shape of seed pod
    • -position of flowers on stem
  4. Hybridization?
    crossing of 2 different true-breds
  5. True-Bread
    all offspring of same variety
  6. Trait?
    variant for a character
  7. Population Sampling
    •Measures frequency of certain traits in a population

    •Use randomly selected group

    –project results for the whole population
  8. Why Is Studying Humans Difficult
    Humans have a long lifespan

    Number of offspring tends to be small

    Can’t conduct breeding experiments
  9. Translocation
    • a chromosomal fragment joins a nonhomologous chromosome.
    • –Some translocations are reciprocal, others are not.
  10. Inversion
    occurs when a chromosomal fragment reattaches to the original chromosome but in the reverse orientation.
  11. Duplication
    occurs when a fragment becomes attached as an extra segment to a sister chromatid
  12. Deletion
    • occurs when a chromosome fragment lacking a centromere is lost during cell division.
    • –This chromosome will be missing certain genes
  13. Down Syndrom
    due to three copies of chromosome 21.

    –Although chromosome 21 is the smallest human chromosome, it severely alters an individual’s phenotype in specific ways
  14. Aneuploidy
    If the organism survives, aneuploidy typically leads to a distinct phenotype
  15. Monosomy
    •Monosomy cells have only one copy of a particular chromosome type

    –Have 2n - 1 chromosomes
  16. Trisomy
    cells have three copies of a particular chromosome type

    – Have 2n + 1 total chromosomes
  17. Human Blood Types
    • •A and B alleles are codominant
    • •O allele is recessive to both A and B
  18. Multiple Alleles
    More than 2 possible alleles for a gene.

    – Ex: human blood types

    •Alleles: A, B and O

    •Phenotypes: A, B, AB, and O
  19. Epistasis
    The effect of one gene on the phenotypic expression of a second gene.

    • – Dog coat color
    • (Yellow all "e")
  20. Polygenic Inheritance
    • An additive effect of two or more genes on a single phenotypic character
    • –Human skin pigmentation and height
  21. Pleiotropy
    • Genes with multiple phenotypic effect.
    • –Sickle-cell anemia

    • –Pigmentation in rats
  22. Co-dominance
    The two alleles are expressed simultaneously.

    –Coloration of cows
  23. Incomplete dominance
    Appearance of offspring is a blend of the phenotypes of the 2 parents.

  24. Imprinted Genes (continued)
    • •All the cells in an individual have genes that are imprinted
    • –Both maternal and paternal imprints are present.

    •During the production of gametes, both maternal and paternal imprints are “erased”.

    • •Then, all chromosomes are “reimprinted” according to the sex of the individual which made the gamete.
  25. Imprinted Genes
    •For most autosomal genes, both alleles are expressed

    •In some cases, only the allele inherited from a particular parent is expressed

    –The ability to express this particular allele is determined in the gametes

    •Methylation of the gene inhibits its expression
  26. Human X-Linked Disorders
    •Color Blindness

    –In humans, color vision receptors in the retina are three different classes of cone cells.

    •Only one type of pigment is present in each class of cone cell.

    –The allele for blue-sensitive is autosomal, but the red- and green-sensitive proteins are on the X chromosome.


    –Bleeding disorder

    •Hemophilia A due to lack of clotting factor IX

    •Hemophilia B due to lack of clotting factor VIII.

    •Muscular Dystrophy

    –Absence of protein dystrophin allows calcium to leak into muscle cells.
  27. Linked Genes
    •Linked genes tend to be inherited together because they are located on the same chromosome

    –Each chromosome has hundreds or thousands of genes.

    –Genes located on the same chromosome, linked genes, tend to be inherited together because the chromosome is passed along as a unit.

    –Results of crosses with linked genes deviate from those expected according to independent assortment.
  28. ´╗┐Sex-Linked gene examples

    –Red/Green Colorblindness



    –Eye color


    –Orange color

    •Calico and Marmelade
  29. Thomas Hunt Morgan
    • 1)Easy to raise
    • 2)Short life span
    • 3)Easy to distinquish contasting traits
    • 4)Produce large numbers of offspring
  30. Chromosome Theory of Inheritance
    •Given that there are hundreds to thousands of traits.

    –There must be more than one gene per chromosome.

    –Therefore, when chromosomes segregate in meiosis, the genes of a chromosome move together.

    •Genes must be linked
  31. Walter S. Sutton
    •Chromosomes and genes are both present in pairs in diploid cells.

    •Homologous chromosomes separate and alleles segregate during meiosis.

    •Fertilization restores the paired condition for both chromosomes and genes
  32. Law of Independent Assortment
    •Each pair of factors segregates independently of the other pairs.

    •All possible combinations of factors can occur in the gametes.
  33. Dihybrid Cross
    • •Mendel performed cross using true-breeding plants differing in two traits.
  34. Recessive Trait
    Trait that fails to appear in the F1 generation
  35. Dominant Trait
    Trait that appears in the F1 Generation
  36. Allele
    Alternate forms of a gene
  37. Phenotype
    Physical appearance of an individual
  38. Genotype
    Genetic makeup of an individual
  39. Law of Segregation
    •Each individual has two factors for each trait.

    •The factors segregate during gamete formation.

    –Each gamete contains only one factor from each pair of factors.

    •Fertilization gives each new individual two factors for each trait.

    •If the two factors differ, then the dominant one is fully expressed in the individual’s appearance; the recessive one has no noticeable effect on the individual’s appearance.
  40. Monohybrid Cross
    • cross-breeding experiments between true-breeding plants.
    • –Chose varieties that differed in only one trait
  41. P2 Generation
    Second Filial generation
  42. P1 generation
    First filial generation
  43. P generation
Card Set
Bio 1.10.11
Bio genes