5: Gene Interactions
Multigene crosses, degrees of dominance, and epistasis in metabolic and genetic pathways.
Monohybrid Cross Genotype-Phenotype Relationships
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Match each of the following parental genotypes in monohybrid crosses with their corresponding descriptions of the progeny.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. Aa × aa | ||
| 2. Aa × Aa | ||
| 3. AA × AA | ||
| 4. AA × Aa | ||
| 5. aa × aa | ||
| 6. AA × aa |
Drag one of the choices below:
- A. Produces a 1:2:1 genotype ratio in progeny
- B. Yields offspring with 50% homozygous dominant and 50% heterozygous genotypes
- C. All offspring have the dominant phenotype and are heterozygous
- D. Produces offspring that are all homozygous recessive
- E. All offspring have the same dominant genotype and phenotype
- F. Produces a 1:1 phenotype ratio in progeny
Monohybrid Cross Genotype Analysis
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Which one of the following parental genotypes in monohybrid crosses correspond to the description of the progeny 'Produces offspring that are all homozygous recessive'.
ABO Blood Group Inheritance Patterns
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For the ABO blood group in humans, the iA and iB alleles are codominant and the i allele is recessive.
A father ♂ with blood type AB has a son ♂ with blood type B.
Which of the following blood types could the mother ♀ possibly have? Check all that apply.
Inheritance Patterns in ABO Blood Group
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For the ABO blood group in humans, the iA and iB alleles are codominant and the i allele is recessive.
If a female ♀ with type O blood marries a male ♂ with type B blood, which of the following blood types could their children possibly have? Check all that apply.
Gene Interaction Types in Dihybrid Crosses
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Above are the phenotypic results from a dihybrid cross and double heterozygote test cross. The phenotypes were nine to seven (9:7).
What type of gene interaction is being shown?
Dihybrid Cross and Epistasis in Metabolic Pathways
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A two step metabolic pathway determines the pigment color. Gene 1 when dominant expresses an enzyme that creates the sky blue pigment from the blue precursor pigment. Gene 2 when dominant expresses an enzyme that creates the tan pigment from the blue precursor pigment. When both genes are dominant, the two enzymes pathways combine to form the new white pigment. If neither of the genes are dominant, then there is no pigment change and the blue precursor pigment remains.
The diagram and description above explain the interaction of two genes. Determine the dihybird cross phenotypic ratio.
Genetic Linkage and Epistasis in Dihybrid Crosses
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In a standard dihybrid cross involving two independent genes, the expected F2 phenotypic ratio is 9:3:3:1. A test-cross with an F1 individual and a double recessive usually yields a 1:1:1:1 phenotypic ratio if the genes assort independently.
In a specific cross, F2 progeny exhibit a modified dihybrid ratio of 10:6 (instead of 9:3:3:1).
What phenotypic ratio would be expected from a test-cross with an individual from the F1 progeny?
Genetic Linkage and Gene Interaction in Dihybrid Crosses
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In a standard dihybrid cross involving two independent genes, the expected F2 phenotypic ratio is 9:3:3:1. A test-cross with an F1 individual and a double recessive usually yields a 1:1:1:1 phenotypic ratio if the genes assort independently.
The progeny from the test-cross exhibited a modified ratio of 2:2, different from the expected 1:1:1:1 ratio.
What phenotypic ratio would be expected in the F2 generation if the original dihybrid cross is continued?
Types of Genetic Dominance in Monohybrid Crosses
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| Gene 1 | Female ♀ | ||
|---|---|---|---|
| G | g | ||
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Male ♂ | G | GG | Gg |
| g | Gg | gg | |
Two organisms were crossed in a monohybrid experiment. The offspring showed three redish pink (■) and one blue (■) phenotype.
What type of dominance best explains these results?
Monohybrid Cross Genotype Outcomes
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Genotype Diversity in Hybrid Crosses
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Genotype Diversity in Hybrid Cross
In a hybrid cross, the range of possible genotypes in the offspring is determined by the genetic makeup of the parental organisms.
Assume that all genes sort independently and display complete dominance.
Hint: For each gene pair from the parents, you can get 1, 2, or 3 unique genotypes.
This is based on the combinations: homozygous x homozygous (1), homozygous x heterozygous (2), and heterozygous x heterozygous (3).
Considering the principle of independent assortment, how many unique GENOTYPES could be produced in a hybrid cross between the following individuals?
| Female (♀) | aa Bb CC Dd EE FF |
| Male (♂) | aa Bb Cc DD EE ff |
Determining Phenotype Diversity in Genetic Crosses
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Phenotype Diversity in Hybrid Cross
In a hybrid cross, you can determine the variety of phenotypes in the offspring by examining the genetic makeup of the parents. Specifically, look at whether each gene can be dominant, recessive, or both.
A dominant gene can mask the effect of its recessive counterpart, thus influencing the number of unique phenotypes.
Hint: To find the number of unique phenotypes, consider each gene pair.
For gene pairs with at least one heterozygous and one either heterozygous or homozygous recessive gene, 2 phenotypes are possible.
For all other combinations, only 1 phenotype is possible.
Assume complete dominance and the principle of independent assortment for all genes.
Given these principles, how many unique PHENOTYPES could result from a hybrid cross between the following individuals?
| Male (♂) | AA Bb Cc DD Ee Ff |
| Female (♀) | Aa Bb Cc DD EE Ff |
Calculating Gamete Diversity through Independent Assortment
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Gamete Diversity in Sexual Reproduction
In sexual reproduction, the potential diversity of gametes – such as sperm and eggs in animals, or pollen and ovules in plants – can be calculated based on the genotype of an individual.
How many unique GAMETES could be produced through the process of independent assortment by an individual with the following genotype?
Hint: Remember, each heterozygous gene pair (like `Aa` or `Bb`) can give rise to two (2) different gametes, while homozygous pairs (like `AA`, `BB`, and `aa`, `bb`) can only give rise to one gamete.
Genotype:Aa bb CC dd ee Ff GG