Biology Flashcards - Genetics

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awc1990
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211253
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Biology Flashcards - Genetics
Updated:
2013-04-03 16:56:33
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Biology Flashcards Genetics
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Biology Flashcards - Genetics Kaplan MCAT B106-B112
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  1. What are alleles?
    Alleles are different forms of the same gene. Alleles occupy the same position on homologous chromosomes.
  2. Define genotype.
    Genotype refers to the genetic makeup of an individual.
  3. Define phenotype.
    Phenotype refers to the physical manifestation of an individual's genotype.
  4. Define homozygous.
    Homozygous individuals have two copies of the same allele for a given trait.
  5. Define heterozygous.
    Heterozygous individuals have two different alleles for a given trait.
  6. Summarize Mendel's First Law (Law of Segregation).
    Mendel's first law states that alleles segregate during meiosis; specifically:

    • *Genes exist in alternative forms (alleles).
    • *An individual inherits two alleles for each trait, one from each parent.
    • *The two alleles segregate during meiosis.
    • *If two different alleles are present, only one will be fully expressed.
  7. Summarize Mendel's Second Law (Law of Independent Assortment).
    Mendel's second law states that alleles of unlinked genes assort independently during meiosis.
  8. Given: P=dominant (purple)  p=recessive (white)

    1. What would be the phenotypic ratio of PPxpp Cross?
    PPxpp = 100% purple

  9. Given: P=dominant (purple)  p=recessive (white)

    2. What would be the phenotypic ratio of PpxPp cross?
    PpxPp = 75% purple: 25% white

  10. Given: P=dominant (purple)  p=recessive (white)

    3. What would be the phenotypic ratio of Ppxpp cross?
    PPxpp = 50% purple : 50% white

  11. Given: P=dominant (purple)  p=recessive (white)

    4. What would be the genotypic ratio of Ppxpp cross?
    Ppxpp = 50% Pp : 50% pp

  12. Given: P=dominant (purple)  p=recessive (white)

    5. What would be the genotypic ratio of a PpxPp cross?
    Pp x Pp = 25% PP: 50% Pp: 25% pp

  13. (T/F) Recombinant frequencies are roughly additive.
    True.
  14. Given: X and Y recombinant frequency = 5%
              X and Z recombinant frequency = 13%

    What is the Y and Z recombinant frequency if the gene order is XYZ?
    8%.
  15. Given: X and Y recombinant frequency = 5%            
              X and Z recombinant frequency = 13%

    What is the Y and Z recombinant frequency if the gene order is YXZ?
    18%.
  16. What is a map unit?
    1 map unit = 1% recombinant frequency.
  17. Red flowers crossed with white flowers yield pink flowers. What kind of dominance is portrayed in this example?
    Incomplete dominance.
  18. Assuming codominance, what happens to the phenotype in the presence of two dominant alleles?
    The phenotype of each allele is simultaneously displayed (e.g., type AB blood).
  19. What is the penetrance of a genotype?
    The penetrance of a genotype is the percentage of individuals in a population who actually express its phenotype.
  20. What is expressivity of a genotype?
    The expressivity of a genotype is the degree to which the phenotype is expressed in an individual.
  21. (T/F) In humans, most sex-linked genes are located on the Y chromosome.
    False, most sex-linked genes are on the X chromosome.
  22. What percentage of daughters will inherit their father's sex-linked gene?
    100% of daughters will inherit their father's sex-linked gene.
  23. What percentage of sons will inherit their father's sex-linked gene?
    0% of sons will inherit their father's sex-linked gene.
  24. What percentage of sons will inherit their mother's sex-linked gene (assuming a heterozygous mother)?
    50% of sons will inherit their mother's sex-linked gene.
  25. (T/F) Females can express a sex-linked recessive trait.
    True, a female carrier and a male with the recessive trait will have a 25% chance of giving birth to a female child with the recessive trait.
  26. What is nondisjunction?
    Nondisjunction is the failure of homologous chromosomes (or sister chromatids) to separate properly during cellular reproduction.
  27. What are the three different results of chromosomal breakage?
    Duplication - The fragment joins with its homologous chromosome.

    Translocation - The fragment joins with a non-homologous chromosome.

    Inversion - The fragment rejoins its original chromosome but in the reverse position.

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