In a Certain Breed of Chicken, an Incomplete Dominant Gene

question 14

Essay

In a certain breed of chicken, an incomplete dominant gene controls color. The homozygous black (BB), when crossed with the homozygous splashed-white (bb), produces an intermediate gray color pattern referred to as blue. A second gene controls the shape of the comb. The dominant allele (R) produces rose, whereas the recessive allele (r) produces single. Give the F1 and F2 genotypic and phenotypic ratios of a cross between a true-breeding black with a single comb and a true-breeding splashed-white with a rose comb.

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Definitions:

Opportunistic Infection

Infection by microorganisms that can cause disease only when a host’s resistance is low.

Microorganism

Minute living organisms, such as bacteria, viruses, fungi, and protozoa, that can be seen only with a microscope.

Endogenous Infection

An infection in which an abnormality or a malfunction in routine body processes causes normally beneficial or harmless microorganisms to become pathogenic.

Asepsis

The absence of bacteria, viruses, and other microorganisms to prevent infection, often referred to in a medical or clinical context.