2. Mendel's Laws of Inheritance

Probability and Genetics

Open Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring:3/8 black: 3/8 cream: 2/8 albino
Open Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring:27/64 gray: 16/64 albino: 9/64 yellow: 9/64 black: 3/64 cream
Open Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring:9/16 gray: 3/16 yellow: 4/16 albino
Open Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring:9/16 gray: 3/16 yellow: 3/16 black: 1/16 cream
Open Question
In pea plants, the appearance of flowers along the main stem is a dominant phenotype called 'axial' and is controlled by an allele T. The recessive phenotype, produced by an allele t, has flowers only at the end of the stem and is called 'terminal.' Pod form displays a dominant phenotype, 'inflated,' controlled by an allele C, and a recessive 'constricted' form, produced by the c allele. A cross is made between a pure-breeding axial, constricted plant and a plant that is pure-breeding terminal, inflated.

Suppose that all of the F₂ progeny with terminal flowers, i.e., plants with terminal flowers and inflated pods and plants with terminal flowers and constricted pods, are saved and allowed to self-fertilize to produce a partial F₃ generation. What is the expected phenotypic distribution among these F₃ plants?
Open Question
In pea plants, the appearance of flowers along the main stem is a dominant phenotype called 'axial' and is controlled by an allele T. The recessive phenotype, produced by an allele t, has flowers only at the end of the stem and is called 'terminal.' Pod form displays a dominant phenotype, 'inflated,' controlled by an allele C, and a recessive 'constricted' form, produced by the c allele. A cross is made between a pure-breeding axial, constricted plant and a plant that is pure-breeding terminal, inflated.

The F₁ progeny of this cross are allowed to self-fertilize. What is the expected phenotypic distribution among the F₂ progeny?
Open Question
If two six-sided dice are rolled, what is the probability that the total number of spots showing is

greater than 5?
Open Question
If two six-sided dice are rolled, what is the probability that the total number of spots showing is

7?
Open Question
If two six-sided dice are rolled, what is the probability that the total number of spots showing is

4?
Open Question
In a species of the cat family, eye color can be gray, blue, green, or brown, and each trait is true breeding. In separate crosses involving homozygous parents, the following data were obtained:Cross P₁ F₁ F₂A green x gray all green 3/4 green: 1/4 grayB green x brown all green 3/4 green: 1/4 brownC. gray x brown. all green 9/16 green: 3/16 brown3/16 gray: 1/16 blueIn a cross between a gray-eyed cat and one of unknown genotype and phenotype, the F₁ generation was not observed. However, the F₂ resulted in the same F₂ ratio as in cross C. Determine the genotypes and phenotypes of the unknown P₁ and F₁ cats.
Open Question
In a species of the cat family, eye color can be gray, blue, green, or brown, and each trait is true breeding. In separate crosses involving homozygous parents, the following data were obtained:Cross P₁ F₁ F₂A green x gray all green 3/4 green: 1/4 grayB green x brown all green 3/4 green: 1/4 brownC. gray x brown. all green 9/16 green: 3/16 brown3/16 gray: 1/16 blueAnalyze the data. How many genes are involved? Define gene symbols and indicate which genotypes yield each phenotype.
Open Question
In a plant, a tall variety was crossed with a dwarf variety. All F₁ plants were tall. When F₁xF₁ plants were interbred, 9/16 of the F₂ were tall and 7/16 were dwarf.What proportion of the F₂ plants will be true breeding if self-fertilized? List these genotypes.
Open Question
In a plant, a tall variety was crossed with a dwarf variety. All F₁ plants were tall. When F₁xF₁ plants were interbred, 9/16 of the F₂ were tall and 7/16 were dwarf.Explain the inheritance of height by indicating the number of gene pairs involved and by designating which genotypes yield tall and which yield dwarf. (Use dashes where appropriate.)
Open Question
In a unique species of plants, flowers may be yellow, blue, red, or mauve. All colors may be true breeding. If plants with blue flowers are crossed to red-flowered plants, all F₁ plants have yellow flowers. When these produced an F₂ generation, the following ratio was observed: 9/16 yellow: 3/16 blue: 3/16 red: 1/16 mauve In still another cross using true-breeding parents, yellow-flowered plants are crossed with mauve-flowered plants. Again, all F₁ plants had yellow flowers and the F₂ showed a 9:3:3:1 ratio, as just shown.Determine the F₁ and F₂ results of a cross between true-breeding red and true-breeding mauve-flowered plants.
Open Question
In a unique species of plants, flowers may be yellow, blue, red, or mauve. All colors may be true breeding. If plants with blue flowers are crossed to red-flowered plants, all F₁ plants have yellow flowers. When these produced an F₂ generation, the following ratio was observed:9/16 yellow: 3/16 blue: 3/16 red: 1/16 mauveIn still another cross using true-breeding parents, yellow-flowered plants are crossed with mauve-flowered plants. Again, all F₁ plants had yellow flowers and the F₂ showed a 9:3:3:1 ratio, as just shown.Describe the inheritance of flower color by defining gene symbols and designating which genotypes give rise to each of the four phenotypes.