Grade 12 Biology: Punnett Squares Worksheet
This worksheet focuses on understanding and applying Punnett Squares to predict genetic outcomes in monohybrid and dihybrid crosses, suitable for Grade 12 Biology students.
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Grade 12 Biology: Punnett Squares Worksheet
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Read each question carefully and answer to the best of your ability. Show all your work for Punnett Square problems.
1. A Punnett square is a diagram that is used to predict the outcome of a particular cross or breeding experiment.
2. An organism with two identical alleles for a trait is said to be , while an organism with two different alleles for a trait is .
3. The observable physical properties of an organism are its , while its genetic makeup is its .
1. In a monohybrid cross between two heterozygous parents (Bb x Bb), what is the expected phenotypic ratio of offspring?
1:1
2:1
3:1
1:2:1
2. Which of the following best describes the purpose of a test cross?
To determine the genotype of a dominant phenotype.
To determine the genotype of a recessive phenotype.
To predict the outcome of a dihybrid cross.
To identify linked genes.
In pea plants, tall (T) is dominant to short (t). Cross a heterozygous tall plant with a short plant.
1. What are the genotypes of the parents?
2. Construct a Punnett square for this cross.
3. What is the expected genotypic ratio of the offspring?
4. What is the expected phenotypic ratio of the offspring?
In guinea pigs, black fur (B) is dominant to brown fur (b), and short hair (S) is dominant to long hair (s). Cross two guinea pigs that are heterozygous for both traits (BbSs x BbSs).
1. What are the possible gametes for each parent?
2. Construct a Punnett square for this dihybrid cross.
3. What is the expected phenotypic ratio of the offspring?
1. A Punnett square can predict the exact number of offspring with a particular genotype.
True
False
2. Incomplete dominance results in a blending of phenotypes in heterozygous individuals.
True
False