Bio 004, College of the Desert

  1. Purebred
    Purebred: Offspring of a single true-breeding variety.
  2. Hybrid
    Hybrid: Offspring of two different true-breeding varieties.
  3. Monohybrid Cross

    Monohybrid (Single Factor) Cross: Situation in which only one characteristic or trait is studied in the P generation and its inheritance pattern.

  4. Hypothesis #1
    • Hypothesis #1: There are alternate forms of heritable traits or genes.

    • Alleles: Alternative forms of the same traits or genes.

    • Example: Eye color (brown and blue).

  5. Hypothesis #2
    • Hypothesis #2: For each characteristic, two alleles are inherited – one from each parent.
    • 1. Homozygous: Two identical alleles for a gene.Example: Eye color (2 brown: 2 blue) – BB: bb.
    • 2. Heterozygous: Two different alleles for a gene. Example: Eye color (1 brown and 1 blue) – Bb.
  6. Hypothesis #3
    • Hypothesis #3: If two alleles of an inherited pair differ, then one determines the organism’s appearance and the other has no noticeable effect on the organism’s appearance.
    • 1. Dominant: Allele that determines the organ-ism’s appearance, masking the other allele (B).
    • 2. Recessive: Allele that has no apparent effect on the organism’s appearance, masked by the other allele (b).
  7. Hypothesis #4

    Hypothesis #4: A sperm or egg carries only one allele for each inherited characteristic because two members of an allele pair segregate from each other during the production of gametes.

  8. Genotype
    Genetic makeup or set of alleles of an organism.
  9. Phenotype
    Physical traits of an organism which are determined by its genetic makeup.
  10. Loci
    (single locus): Specific locations of genes along the chromosome
  11. Dihybrid Cross

    (Double Factor) : Situation in which two characteristics or traits are studied in the P generation and their inheritance pattern.

  12. Hypothesis #1

    Hypothesis #1: Each pair of alleles assorts independently of the other pairs of alleles during gamete formation.

  13. Rule of Multiplication

    The probability of a compound event is the product of separate probabilities of the independent event.

  14. Wild-type Traits
    • Wild-type Traits: Those traits most often observed in nature.

    • 1. Not always specified by dominant alleles.

    • 2. Example: Five fingers in humans (recessive trait).

  15. Carrier
    • Carrier: Those with one allele for a recessive disorder, yet who do not exhibit symptoms.

    • 1. Example: albinism

    • 2. Table 9.1, p. 155 – Some Autosomal Disorders in Humans.

  16. Recessive Disorders
    • Recessive Disorders

    • 1. Most human genetic disorders are recessive.

    • 2. Relatively harmless to lethal disease.

    • 3. Follow Mendel’s laws.

    • 4. Usually inherited from carrier parents.

    • 5. Example: Sickle Cell Anemia in Humans.

    • 6. Inbreeding: Mating of closely related individuals

    • a. Increases chances that offspring will be homozygous for a recessive disorder.

    • b. Example: dogs – hip dysplasia.

  17. Dominant Disorders
    • Dominant Disorders

    • 1. Relatively harmless to lethal diseases.

    • 2. Rarer than recessive disorders because of a parent being

    • affected by condition.
    • a. Not likely to be passed on to offspring.

    • 3. Example: achondroplasia.

  18. Incomplete Dominance

    When the phenotype of a heterozygote is intermediate between two ozygotes (blended).Example: Pink rose

  19. Codominance

    When both alleles are found in a heterozygous state and their effects are simultaneously expressed. Example: Roan cattle.

  20. Multiple Alleles

    When more than two alleles for a single trait are present.Example: Blood type (A and B are both dominant while O is recessive).

  21. Pleiotropy
    • One gene, many traits!

    • Multiple effects a single gene may have on a number of different phenotypic characteristics Example: Sickle Cell Anemia.

  22. Polygenic Inheritance

    Additive effects of two or more genes on a single phenotypic characteristic. Example: Figure 9.22, p. 161 – A Model for Polygenic Inheritance for Skin Color.

  23. Chromosome Basis of Inheritance
    Genes are located at specific positions on chromosomes and that the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns.
  24. Linked Genes
    • Genes which are located close together on a chromosome and are inherited as a set.

    • 1. Do not follow Mendel’s law of Independent assortment.

    • 2. Example: hair color + eye color.

  25. Female sex chromosomes
    • XX
    • (each egg carries one X chromosome)
  26. Male sex chromosomes
    XY (Each sperm carries one X or one Y chromosome).
  27. Sex-linked Gene
    gene unrelated to maleness or femaleness located on one of the sex chromosomes.
  28. Sex-linked Disorders in Humans
    • 1. Hemophilia

    • 2. Red-green Colorblindness

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Bio 004, College of the Desert
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