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.

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. 

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?

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?

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?

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?