Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:

9/16 brown : 3/16 black : 4/16 albino

Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:

3/8 black : 3/8 cream : 2/8 albino

Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:

27/64 brown : 16/64 albino : 9/64 yellow : 9/64 black : 3/64 cream

Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:

3/4 brown : 1/4 yellow

Total cholesterol in blood is reported as the number of milligrams (mg) of cholesterol per 100 milliliters (mL) of blood. The normal range is 180–220 mg/100 mL. A gene mutation altering the function of cell-surface cholesterol receptors restricts the ability of cells to collect cholesterol from blood and draw it into cells. This defect results in elevated blood cholesterol levels. Individuals who are heterozygous for a mutant allele and a wild-type allele have levels of 300–600 mg/100 mL, and those who are homozygous for the mutation have levels of 800–1000 mg/100 mL. Identify the genetic term that best describes the inheritance of this form of elevated cholesterol level, and justify your choice.

Flower color in snapdragons results from the amount of the pigment anthocyanin in the petals. Red flowers are produced by plants that have full anthocyanin production, and ivory-colored flowers are produced by plants that lack the ability to produce anthocyanin. The allele An1 has full activity in anthocyanin production, and the allele An2 is a null allele. Dr. Ara B. Dopsis, a famous genetic researcher, crosses pure-breeding red snapdragons to pure-breeding ivory snapdragons and produces F₁ progeny plants that have pink flowers. He proposes that this outcome is the result of incomplete dominance, and he crosses the F₁ to test his hypothesis. What phenotypes does Dr. Dopsis predict will be found in the F₂, and in what proportions?

A plant line with reduced fertility comes to the attention of a plant breeder who observes that seed pods often contain a mixture of viable seeds that can be planted to produce new plants and withered seeds that cannot be sprouted. The breeder examines numerous seed pods in the reduced fertility line and counts 622 viable seeds and 204 nonviable seeds.

What single-gene mechanism best explains the breeder's observation?

A plant line with reduced fertility comes to the attention of a plant breeder who observes that seed pods often contain a mixture of viable seeds that can be planted to produce new plants and withered seeds that cannot be sprouted. The breeder examines numerous seed pods in the reduced fertility line and counts 622 viable seeds and 204 nonviable seeds.

Propose an additional experiment to test the genetic mechanism you propose. If your hypothesis is correct, what experimental outcome do you predict?

In cattle, an autosomal mutation called Dexter produces calves with short stature and short limbs. Embryos that are homozygous for the Dexter mutation have severely stunted development and either spontaneously abort or are stillborn. What progeny phenotypes do you expect from the cross of two Dexter cows? What are the expected proportions of the expected phenotypes?

The coat color in mink is controlled by two codominant alleles at a single locus. Red coat color is produced by the genotype R₁R₁, silver coat by the genotype R₁R₂, and platinum color by R₂R₂. White spotting of the coat is a recessive trait found with the genotype ss. Solid coat color is found with the S– genotype.

What are the expected progeny phenotypes and proportions for the cross SsR₁R₂ x ssR₂R₂?

The coat color in mink is controlled by two codominant alleles at a single locus. Red coat color is produced by the genotype R₁R₁, silver coat by the genotype R₁R₂, and platinum color by R₂R₂. White spotting of the coat is a recessive trait found with the genotype ss. Solid coat color is found with the S– genotype.

If the cross SsR₁R₂ x SsR₁R₁ is made, what are the progeny phenotypes, and in what proportions are they expected to occur?

The coat color in mink is controlled by two codominant alleles at a single locus. Red coat color is produced by the genotype R₁R₁, silver coat by the genotype R₁R₂, and platinum color by R₂R₂. White spotting of the coat is a recessive trait found with the genotype ss. Solid coat color is found with the S– genotype.

Two crosses are made between mink. Cross 1 is the cross of a solid, silver mink to one that is solid, platinum. Cross 2 is between a spotted, silver mink and one that is solid, silver. The progeny are described in the table below. Use these data to determine the genotypes of the parents in each cross. 

Strains of petunias come in four pure-breeding colors: white, blue, red, and purple. White petunias are produced when plants synthesize no flower pigment. Blue petunias and red petunias are produced when plants synthesize blue or red pigment only. Purple petunias are produced in plants that synthesize both red and blue pigment (the mixture of red and blue makes purple). Flower-color pigments are synthesized by gene action in two separate pigment-producing biochemical pathways. Pathway I contains gene A that produces an enzyme to catalyze conversion of a colorless pigment designated to blue pigment. In Pathway II, the enzymatic product of gene B converts the colorless pigment designated to red pigment. The two genes assort independently.

What are the possible genotype(s) for pure-breeding red petunias? 

Strains of petunias come in four pure-breeding colors: white, blue, red, and purple. White petunias are produced when plants synthesize no flower pigment. Blue petunias and red petunias are produced when plants synthesize blue or red pigment only. Purple petunias are produced in plants that synthesize both red and blue pigment (the mixture of red and blue makes purple). Flower-color pigments are synthesized by gene action in two separate pigment-producing biochemical pathways. Pathway I contains gene A that produces an enzyme to catalyze conversion of a colorless pigment designated to blue pigment. In Pathway II, the enzymatic product of gene B converts the colorless pigment designated to red pigment. The two genes assort independently.

What are the possible genotype(s) for true-breeding blue petunias? 

Strains of petunias come in four pure-breeding colors: white, blue, red, and purple. White petunias are produced when plants synthesize no flower pigment. Blue petunias and red petunias are produced when plants synthesize blue or red pigment only. Purple petunias are produced in plants that synthesize both red and blue pigment (the mixture of red and blue makes purple). Flower-color pigments are synthesized by gene action in two separate pigment-producing biochemical pathways. Pathway I contains gene A that produces an enzyme to catalyze conversion of a colorless pigment designated to blue pigment. In Pathway II, the enzymatic product of gene B converts the colorless pigment designated to red pigment. The two genes assort independently.

True-breeding red petunias are crossed to pure-breeding blue petunias, and all the F₁ progeny have purple flowers. If the F₁ are allowed to self-fertilize and produce the F₂, what is the expected phenotypic distribution of the F₂ progeny? Show your work.

Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from the production of one colored pigment, and white results from the absence of pigment production.

What is the genotype of a pure-breeding purple parakeet strain? 

Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from the production of one colored pigment, and white results from the absence of pigment production.

What is the genotype of a pure-breeding yellow strain of parakeet? 

Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from the production of one colored pigment, and white results from the absence of pigment production.

If a pure-breeding blue strain of parakeet (aa BB CC DD) is crossed to one that is pure-breeding purple, predict the genotype(s) and phenotype(s) of the F₁. Show your work

Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from production of one colored pigment, and white results from absence of pigment production.

If F₁ birds identified in part (c) are mated at random, what phenotypes do you expect in the F₂ generation? What are the ratios among phenotypes? Show your work. 

Brachydactyly type D is a human autosomal dominant condition in which the thumbs are abnormally short and broad. In most cases, both thumbs are affected, but occasionally just one thumb is involved. The accompanying pedigree shows a family in which brachydactyly type D is segregating. Filled circles and squares represent females and males who have involvement of both thumbs. Half-filled symbols represent family members with just one thumb affected.

Is there any evidence of variable expressivity in this family? Explain. 

Brachydactyly type D is a human autosomal dominant condition in which the thumbs are abnormally short and broad. In most cases, both thumbs are affected, but occasionally just one thumb is involved. The accompanying pedigree shows a family in which brachydactyly type D is segregating. Filled circles and squares represent females and males who have involvement of both thumbs. Half-filled symbols represent family members with just one thumb affected.

Is there evidence of incomplete penetrance in this family? Explain. 

A male and a female mouse are each from pure-breeding albino strains. They have a litter of 10 pups, all of which have normal pigmentation. The F₁ pups are crossed to one another to produce 56 F₂ mice, of which 31 are normally pigmented and 25 are albino.

Using clearly defined allele symbols of your own choosing, give the genotypes of parental and F₁ mice. What genetic phenomenon explains these parental and F₁ phenotypes?

A male and a female mouse are each from pure-breeding albino strains. They have a litter of 10 pups, all of which have normal pigmentation. The F₁ pups are crossed to one another to produce 56 F₂ mice, of which 31 are normally pigmented and 25 are albino.

What genetic phenomenon explains the F₂ results? Use your allelic symbols to explain the F₂ results.

Xeroderma pigmentosum (XP) is an autosomal recessive condition characterized by moderate to severe sensitivity to ultraviolet (UV) light. Patients develop multiple skin lesions on UV-exposed skin, and skin cancers often develop as a result. XP is caused by deficient repair of DNA damage from UV exposure. Many genes are known to be involved in repair of UV-induced DNA damage, and several of these genes are implicated in XP. What genetic phenomenon is illustrated by XP?

Xeroderma pigmentosum (XP) is an autosomal recessive condition characterized by moderate to severe sensitivity to ultraviolet (UV) light. Patients develop multiple skin lesions on UV-exposed skin, and skin cancers often develop as a result. XP is caused by deficient repair of DNA damage from UV exposure.

A series of 10 skin-cell lines was grown from different XP patients. Cells from these lines were fused, and the heterokaryons were tested for genetic complementation by assaying their ability to repair DNA damage caused by a moderate amount of UV exposure. In the table below, '+' indicates that the fusion cell line performs normal DNA damage mutation repair, and '−' indicates defective DNA repair. Use this information to determine how many DNA-repair genes are mutated in the 10 cell lines, and identify which cell lines share the same mutated genes. 

Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

For what number of genes are variable alleles segregating in the G₁ x Y cross? The G₂ x Y cross? In the G₃ x Y cross? Explain your rationale for each answer. 

Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

Using the allele symbols A and a, B and b, and D and d to represent alleles at segregating genes, give the genotypes of parental and F₁ plants in each cross. 

Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

For each set of F₂ progeny, provide a genetic explanation for the yellow : green ratio. What are the genotypes of yellow and green F₂ lentil plants in the G₂ x Y cross? 

Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

If green-seeded strains G₁ and G₃ are crossed, what are the phenotype and the genotype of F₁ progeny? 

Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

What proportion of the F₂ are expected to be green? Show your work.