Question

Scientists discover that colder climates, areas averaging 0 to 15°C, trigger a "bleaching effect" on the epistatic gene E/e. This gene works in conjunction with the fur color gene B/b in Labrador retrievers. In more temperate climates, the (B) black fur gene dominates the (b) brown fur gene so that only the (bb) genotype produces brown Labs. In contrast, the E/e gene, which determines how much pigment gets deposited on the fur, is altered chemically by sustained cold weather. Normally, the dominant expression of this pigment gene (EE or Ee) allows the black or brown pigment to adhere to the fur. In warm climates, the recessive allele combination, (ee), alters pigmentation to produce only yellow Labs. The bleaching effects that colder climate has on pigmentation expression may be expressed as: (EE) no effect on pigmentation; black or brown fur depends on the fur coat genotype. (Ee) slight bleaching on pigmentation. Black fur changes to roan (reddish-brown) fur, and brown fur becomes gray. (ee) total bleaching effect on pigmentation; yellow fur now appears white. Mr. Johnson has an entire breeding stock of heterozygous black Labs (BbEe). He wants to breed his animals in a location that can take advantage of this environmental change on the new coat colors produced. If Mr. Johnson moves to Alaska, what color of Labrador retriever can he expect to produce the least of in his first generation of offspring?

Answer 1

The least phenotype he can expect to produce in his first generation of offspring is BROWN

Step-by-step explanation:

Available data:

• The gene that codifies for fur color has two alleles. Dominant allele B, and recessive allele b
• The gene that codifies for the presence or absence of color has the dominant allele E and the recessive allele e.
• Both genes work in conjunction

In temperate climates

• Individuals with Genotypes BBEE / BBEe / BbEE / BbEe are BLACK
• Individuals with Genotypes bbEE / bbEe are BROWN
• Individuals with Genotypes BBee / Bbee / bbee are YELLOW

In cold climates

• Individuals with Genotypes BBEE / BbEE are BLACK
• Individuals with Genotypes BBEe / BbEe are ROAN
• Individuals with Genotypes bbEE are BROWN
• Individuals with Genotypes bbEe are GRAY
• Individuals with Genotypes BBee / Bbee / bbee are WHITE

Cross:

Parentals) BbEe x BbEe

Phenotypes) Black Black

Gametes) BE Be bE be BE Be bE be

Punnett Square)

BE Be bE be

BE BBEE BBEe BbEE BbEe

Be BBEe BBee BbEe Bbee

bE BbEE BbEe bbEE bbEe

be BbEe Bbee bbEe bbee

F1) Genotype and Phenoype

• 1/16 BBEE Black individuals
• 2/16 BbEE, Black individuals
• 1/16 bbEE, Brown individuals
• 2/16 BBEe, Roan individuals
• 4/16 BbEe, Roan inviduals
• 2/16 bbEe, Gray individuals
• 1/16 BBee, White individuals
• 2/16 Bbee, White individuals
• 1/16 bbee, White individuals

Total phenotypic proportions

• 3/16 black dogs
• 1/16 brown dog
• 6/16 Roan dogs
• 2/16 Gray dogs
• 4/16 white dogs.