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Test Crosses exam
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  • Test Cross

    A method used to determine the genotype of an organism with a dominant phenotype by crossing it with a homozygous recessive organism.

  • What is the purpose of a test cross?

    To determine the genotype of an organism with a dominant phenotype.

  • Homozygous Dominant

    An organism with two dominant alleles for a trait (e.g., YY).

  • Heterozygous

    An organism with one dominant and one recessive allele for a trait (e.g., Yy).

  • What does it mean if all offspring display the dominant phenotype in a test cross?

    The mystery parent is homozygous dominant.

  • Homozygous Recessive

    An organism with two recessive alleles for a trait (e.g., yy).

  • What does a mix of phenotypes in the offspring indicate in a test cross?

    The mystery parent is heterozygous.

  • Phenotype

    The observable traits of an organism.

  • Genotype

    The genetic makeup of an organism.

  • What are the three steps to performing a test cross?

    1. Cross the mystery parent with a homozygous recessive parent. 2. Analyze the offspring phenotypes. 3. Make a conclusion about the mystery parent's genotype.

  • Dominant Allele

    An allele that expresses its phenotype even in the presence of a recessive allele.

  • Recessive Allele

    An allele that only expresses its phenotype when paired with another recessive allele.

  • What is the genotype of a yellow pea plant if all offspring are yellow in a test cross?

    Homozygous dominant (YY).

  • What is the genotype of a yellow pea plant if the offspring are 50% yellow and 50% green in a test cross?

    Heterozygous (Yy).

  • Cross Fertilization

    The process of fertilizing one plant with the pollen from another plant.

  • What does a 100% dominant phenotype in offspring suggest about the mystery parent's genotype?

    The mystery parent is homozygous dominant.

  • What does a 50% dominant and 50% recessive phenotype in offspring suggest about the mystery parent's genotype?

    The mystery parent is heterozygous.

  • Allele

    A variant form of a gene.

  • What is the role of a homozygous recessive parent in a test cross?

    To provide a known genotype for comparison.

  • Why can't phenotype alone determine genotype?

    Because a dominant phenotype can result from either a homozygous dominant or heterozygous genotype.

  • What does a test cross reveal about genetic inheritance?

    It helps understand the role of alleles in determining traits.

  • Why is a homozygous recessive parent used in a test cross?

    Because its genotype is known and it can reveal the genotype of the mystery parent.

  • What is the significance of analyzing offspring phenotypes in a test cross?

    It helps determine the genotype of the mystery parent.

  • What does a dominant phenotype indicate about an organism's alleles?

    The organism has at least one dominant allele.

  • What is the genotype of a green pea plant?

    Homozygous recessive (yy).