Genetics - Inheritance

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jdonaldson
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4950
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Genetics - Inheritance
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2010-02-26 09:56:48
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genetics inheritance usp bruist james donaldson
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Genetics chapter on inheritance.
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  1. Gregor Mendel used what organism for his experiments on inheritance?
    Pisum Sativum, a pea plant.
  2. Why was the pea plant a good choice for inheritance experiments?
    • 1.) It was a fast growing plant, therefore many generations could be grown in a single season.
    • 2.) Cross pollination allowed for easily controlled breeding.
    • 3.) The traits were unambiguous, that is, they were easily distinguishable.
    • 4.) True breeding strains could be developed (homozygous).
  3. Mendel learned that observed phenotypes are a result of what?
    The genotype of an organism resulting from the genes/alleles inherited from the offspring's parents.
  4. F0:
    Father bred true dominant.
    Mother bred true recessive.

    What percentage of the F1 offspring will show the recessive trait?
    0%

    • The resulting offspring exhibit the dominant trait 100%.
    • F1 is all heterozygous.
  5. F0 generation:

    Father is heterozygous.
    Mother is heterozygous.

    Describe the F1 generation.
    F1:

    • 75% exhibit the dominant trait. 1/3 of those breed true (homozygous dominant).
    • 25% exhibit the recessive trait, having bred true (homozygous recessive)/
  6. Explain the difference between:
    genotype and phenotype.
    • Genotype: the genetic makeup of an organism (in regards to one or many genes).
    • Phenotype: the physical, observable result of the expression of an organisms genotype(s).
  7. Explain the law of independent assortment.
    • The expression of one trait does not affect the expression of another.
    • In the example of the pea plants, plant height does not affect seed color.
  8. What is a gene?
    A segment of DNA that codes for the sequence of amino acids in a single protein (or nucleotides for a functional RNA).
  9. Define penetrance.
    • The extent to which a gene or set of genes is expressed in the phenotypes of the individuals carrying it.
    • It is measured by the proportion of carriers who show the characteristic phenotype.
  10. Describe complementation groups based on the following illustration.
  11. Explain complementation.
    When two different strains of an organism contain mutations on genes that code for different enzymes in the same metabollic pathway. Since its the same pathway, both strains show the same mutated phenotype, despite that the malfunctioning enzymes are different.

    Some of their offspring, however, may receive the right combination of genes for the correct enzymes and will thus have a working pathway and recover the wild-type phenotype.
  12. What are the four phases of the cell cycle?
    • 1.) Gap 1 (G1)
    • 2.) Synthesis (S)
    • 3.) Gap 2 (G2)
    • 4.) Mitosis (M)
  13. How many strands of DNA does one chromosome have:
    1.) Before the "S" phase?
    2.) After the "S" phase?
    • 1.) One strand
    • 2.) Two strands - one strand per "sister" chromatid
  14. Interphase is composed of what phases of the cell cycle?
    G1, S, & G2
  15. Which phase is the shortest of the entire cell cycle?
    Mitosis.
  16. During interphase, the cell is producing proteins and organelles, but DNA is only duplicated during the ______ phase.
    The "synthesis" phase.
  17. During which phases of the cell cycle is the cell 4n?
    From the "synthesis" phase to just before division during Mitosis.
  18. What process gives rise to two diploid cells from one diploid cell?
    Mitosis.
  19. What process gives rise to four haploid cells from one diploid cell?
    Meiosis.
  20. In which phase of Mitosis do the chromosomes condense, revealing sister chromatids?
    Prophase.
  21. During which phase does the nuclear envelope disappear and the chromosomes align at the equitorial plate?
    Metaphase.
  22. During which phase do the sister chromatids separate?
    Anaphase.
  23. During which phase does the cell go through cytokinesis and the nuclear envelopes reappear?
    Telophase.
  24. In meiosis, crossing over happens during which phase?
    Prophase 1.
  25. During which phase of meiosis do the chromosomes condense?
    Prophase 1.
  26. During which phase of meiosis do the chromosomes separate, keeping their sister chromatids paired?
    Anaphase 1.
  27. When does DNA synthesis not occur naturally during the Interphase stage?
    During Interphase 2 of meiosis.
  28. Define autosomal chromosome.
    A non-sex related chromosome.
  29. True or false:
    All genes assort independently.
    • False.
    • Some genes are linked.
  30. What determines the likelihood that two genes are linked - that is, they will be inherited together?
    Their proximity to one another on a given chromosome. The closer they are, the more likely they will be inherited together (having crossed over together during prophase 1).

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