Monohybrid And Dihybrid Crosses

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Monohybrid And Dihybrid Crosses - Quiz

Show me that you understand how to predict the possible outcome of mono and dihybrid crosses using Punnett squares.
Use the following letters for your crosses: T = tall t = short G = green seeds g = yellow seeds P = purple flowers p = white flowers


Questions and Answers
  • 1. 

    A purebred pea plant for height is crossed with a hybrid for height. The phenotypic ratio is 4:0.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    When a purebred pea plant for height is crossed with a hybrid for height, the phenotypic ratio of 4:0 indicates that all of the offspring have the same phenotype as the purebred parent. This suggests that the trait for height is dominant and the hybrid parent is heterozygous for the trait. Therefore, the statement is true.

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  • 2. 

    Check all the possible combinations of alelles in this pea plant's pollen:    TtPp

    • A.

      TP

    • B.

      Tp

    • C.

      TT

    • D.

      Tp

    • E.

      TP

    • F.

      PP

    Correct Answer(s)
    A. TP
    B. Tp
    D. Tp
    E. TP
    Explanation
    The given question is asking for all possible combinations of alleles in the pollen of a pea plant with the genotype TtPp. The genotype TtPp represents two different genes, with T and t representing one gene and P and p representing another gene. Each gene has two alleles, uppercase and lowercase. The possible combinations of alleles in the pollen are TP, Tp, tp, and tP.

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  • 3. 

    A homozygous recessive plant has two copies of the ____________________ allele.

    Correct Answer(s)
    recessive
    Explanation
    A homozygous recessive plant has two copies of the recessive allele. This means that both of the plant's alleles for a particular trait are the same and are recessive. In genetics, alleles are alternative forms of a gene that determine specific traits. Recessive alleles are only expressed when an individual has two copies of the same recessive allele. Therefore, in this case, the plant has two copies of the recessive allele, resulting in the expression of the recessive trait.

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  • 4. 

    The ___________________ of the organism is what you can see.

    Correct Answer(s)
    phenotype
    Explanation
    The term "phenotype" refers to the observable characteristics or traits of an organism. These traits can include physical features, such as eye color or height, as well as behavioral or physiological characteristics. The phenotype is determined by a combination of genetic factors and environmental influences. It is what can be seen or observed in an organism, as opposed to the genotype, which refers to the genetic makeup or underlying genes of the organism.

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  • 5. 

    The __________________________ of the organism is what is in the genes.

    Correct Answer(s)
    genotype
    Explanation
    The term "genotype" refers to the genetic makeup of an organism. It represents the specific combination of genes that an individual possesses. Genes are the units of heredity that are responsible for the traits and characteristics of an organism. Therefore, the genotype of an organism is the genetic information that is encoded in its genes. This information determines the physical and biological traits that an organism will exhibit.

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  • 6. 

    Perform the following cross and check the boxes for the correct phenotypic and genotypic ratios.
    • a heterozygous green seeded plant crossed with a purebred recessive for seed color

    • A.

      Phenotypic ratio 2:2

    • B.

      Genotypic ratio 2:2

    • C.

      Phenotypic ratio 1:3

    • D.

      Genotypic ratio 1:3

    • E.

      Phenotypic ratio 1:2:1

    • F.

      Genotypic ratio 1:2:1

    Correct Answer(s)
    A. Phenotypic ratio 2:2
    B. Genotypic ratio 2:2
    Explanation
    The given correct answer suggests that when a heterozygous green seeded plant is crossed with a purebred recessive for seed color, the phenotypic ratio is 2:2, meaning that there is an equal chance of obtaining green seeded plants and recessive plants. Similarly, the genotypic ratio is also 2:2, indicating that there is an equal chance of obtaining the heterozygous genotype and the recessive genotype.

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  • 7. 

    In the following dihybrid cross there is no need to fill out the whole sixteen square table to determine the outcome.
    • TtGg  x  ttgg

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    In a dihybrid cross, two traits are being crossed and the outcome can be determined by looking at the phenotypic ratios of the offspring. In this case, the traits being crossed are TtGg and ttgg. The genotype of the first parent is known, and the genotype of the second parent is known as well. Since the traits are not linked and are independently assorting, the outcome can be determined by looking at the possible combinations of alleles for each trait. This can be done without filling out the entire sixteen square table, as the phenotypic ratios can be determined from the known genotypes. Therefore, the statement is true.

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  • 8. 

    When a purebred recessive plant is crossed with a plant with the dominant phenotype you can find out if the second plant is a hybrid or a purebred by looking at the possible offspring. Choose the correct allele combinations of the offspring if the unknown plant's genotype is homozygous dominant.

    • A.

      All four of the offspring will have the dominant phenotype

    • B.

      One will have the dominant phenotype and three will have the recessive

    • C.

      Two will show the dominant phenotype and two the recessive

    • D.

      One will have the recessive phenotype and three the dominant

    Correct Answer
    A. All four of the offspring will have the dominant phenotype
    Explanation
    If the unknown plant's genotype is homozygous dominant, it means that both of its alleles for the gene in question are dominant. When this plant is crossed with a purebred recessive plant, all of the offspring will inherit one dominant allele from the unknown plant and one recessive allele from the purebred recessive plant. Since the dominant allele is always expressed over the recessive allele, all four of the offspring will have the dominant phenotype.

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  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • May 04, 2012
    Quiz Created by
    Despinoza

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