Genetic Crossing

What is the genotype of a homozygous dominant individual for a trait where "A" is the dominant allele?

• aa

• AA

• Aa

• aA

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DOK Level 1: Recall

In a monohybrid cross, what is the expected phenotypic ratio of the offspring when both parents are heterozygous for a trait?

• 1:1

• 3:1

• 1:2:1

• 9:3:3:1

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DOK Level 1: Recall

Which of the following represents a heterozygous genotype?

• AA

• aa

• Aa

• aA

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DOK Level 1: Recall

If a plant with genotype Aa is crossed with a plant with genotype aa, what percentage of the offspring will have the genotype Aa?

• 0%

• 25%

• 50%

• 100%

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DOK Level 2: Skill/Concept

In a monohybrid cross, if a homozygous dominant individual (AA) is crossed with a homozygous recessive individual (aa), what will be the genotype of all the offspring?

• AA

• Aa

• aa

• aA

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DOK Level 2: Skill/Concept

Given a monohybrid cross between two heterozygous individuals (Aa x Aa), what is the probability of obtaining an offspring with the recessive phenotype?

• 0%

• 25%

• 50%

• 75%

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DOK Level 2: Skill/Concept

Explain why a monohybrid cross between two heterozygous individuals (Aa x Aa) results in a 3:1 phenotypic ratio.

• Because dominant alleles always mask recessive alleles.

• Because each parent can pass on either the dominant or recessive allele, leading to three possible genotypes.

• Because the dominant allele is more likely to be passed on.

• Because the recessive allele is less likely to be passed on.

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DOK Level 3: Strategic Thinking

A plant with genotype Aa is crossed with another plant with genotype Aa. Using a Punnett square, determine the genotypic ratio of the offspring.

• 1 AA : 2 Aa : 1 aa

• 3 AA : 1 aa

• 1 AA : 1 Aa : 2 aa

• 2 AA : 2 Aa

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DOK Level 3: Strategic Thinking

If a monohybrid cross between two heterozygous individuals (Aa x Aa) results in 75% of the offspring displaying the dominant phenotype, explain the genetic basis for this observation.

• The dominant allele is more common in the population.

• The dominant allele masks the effect of the recessive allele in heterozygous individuals.

• The recessive allele is less likely to be inherited.

• The dominant allele is stronger than the recessive allele.

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DOK Level 3: Strategic Thinking

Describe the process of setting up and interpreting a Punnett square for a monohybrid cross between a homozygous dominant individual (AA) and a heterozygous individual (Aa).

• Place the alleles of one parent on the top and the alleles of the other parent on the side, then fill in the squares to show possible genotypes of the offspring.

• Place the alleles of one parent on the top and the alleles of the other parent on the side, then fill in the squares to show possible phenotypes of the offspring.

• Place the alleles of one parent on the top and the alleles of the other parent on the side, then fill in the squares to show possible genotypes and phenotypes of the offspring.

• Place the alleles of one parent on the top and the alleles of the other parent on the side, then fill in the squares to show the probability of each genotype.

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DOK Level 3: Strategic Thinking