Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 4 - Extensions of Mendelian Genetics
Klug - Concepts of Genetics  12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
Chapter 4, Problem 14b

Horses can be cremello (a light cream color), chestnut (a brownish color), or palomino (a golden color with white in the horse's tail and mane). Of these phenotypes, only palominos never breed true.
Probabilities of offspring coat colors from matings: cremello × palomino, chestnut × palomino, and palomino × palomino.
Predict the F1 and F2 results of many initial matings between cremello and chestnut horses.

Verified step by step guidance
1
Step 1: Identify the genotypes corresponding to each horse color phenotype. Cremello is homozygous for the cream allele (let's denote it as CC), chestnut is homozygous recessive (cc), and palomino is heterozygous (Cc).
Step 2: Determine the F1 generation from a cross between cremello (CC) and chestnut (cc). Use a Punnett square to combine the alleles from each parent: all offspring will be heterozygous (Cc), which corresponds to the palomino phenotype.
Step 3: For the F2 generation, cross two F1 palomino horses (Cc × Cc). Use a Punnett square to find the genotypic ratios: 1 CC (cremello), 2 Cc (palomino), and 1 cc (chestnut).
Step 4: Translate the genotypic ratios into phenotypic ratios for the F2 generation: 1/4 cremello, 1/2 palomino, and 1/4 chestnut.
Step 5: Summarize the results: F1 offspring from cremello × chestnut matings are all palomino, while the F2 generation shows a 1:2:1 phenotypic ratio of cremello, palomino, and chestnut, respectively.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Incomplete Dominance

Incomplete dominance occurs when neither allele is completely dominant, resulting in a heterozygous phenotype that is a blend of the two homozygous phenotypes. In horses, the palomino coat color is an example, where crossing a chestnut and a cremello produces a palomino, a mix of the two colors.
Recommended video:
Guided course
04:37
Variations on Dominance

Genotype and Phenotype Ratios in Crosses

Predicting offspring involves understanding genotype combinations and their corresponding phenotypes. For example, crossing cremello and chestnut horses produces palomino offspring, and analyzing F1 and F2 generations requires calculating expected ratios based on Mendelian inheritance patterns.
Recommended video:
Guided course
07:52
Gamete Genotypes

Breeding True vs. Segregation of Alleles

Breeding true means offspring consistently show the parent's phenotype, indicating homozygosity. Palominos do not breed true because they are heterozygous, producing a mix of cremello, chestnut, and palomino offspring in subsequent generations due to allele segregation.
Recommended video:
Guided course
10:15
Genetic Drift
Related Practice
Textbook Question

Three gene pairs located on separate autosomes determine flower color and shape as well as plant height. The first pair exhibits incomplete dominance, where the color can be red, pink (the heterozygote), or white. The second pair leads to personate (dominant) or peloric (recessive) flower shape, while the third gene pair produces either the dominant tall trait or the recessive dwarf trait. Homozygous plants that are red, personate, and tall are crossed to those that are white, peloric, and dwarf. Determine the F₁ genotype(s) and phenotype(s). If the F₁ plants are interbred, what proportion of the offspring will exhibit the same phenotype as the F₁ plants?

827
views
Textbook Question

Flower color may be red, white, or pink, and flower shape may be personate or peloric. For the following crosses, determine the P₁ and F₁ genotypes:

549
views
Textbook Question

Horses can be cremello (a light cream color), chestnut (a brownish color), or palomino (a golden color with white in the horse's tail and mane). Of these phenotypes, only palominos never breed true.

From the results given above, determine the mode of inheritance by assigning gene symbols and indicating which genotypes yield which phenotypes.

1086
views
Textbook Question

With reference to the eye color phenotypes produced by the recessive, autosomal, unlinked brown and scarlet loci in Drosophila, predict the F₁ and F₂ results of the following P₁ crosses. (Recall that when both the brown and scarlet alleles are homozygous, no pigment is produced, and the eyes are white.)

Wild type x White

562
views
Textbook Question

With reference to the eye color phenotypes produced by the recessive, autosomal, unlinked brown and scarlet loci in Drosophila, predict the F₁ and F₂ results of the following P₁ crosses. (Recall that when both the brown and scarlet alleles are homozygous, no pigment is produced, and the eyes are white.)

Wild type x Scarlet

649
views
Textbook Question

With reference to the eye color phenotypes produced by the recessive, autosomal, unlinked brown and scarlet loci in Drosophila, predict the F₁ and F₂ results of the following P₁ crosses. (Recall that when both the brown and scarlet alleles are homozygous, no pigment is produced, and the eyes are white.)

Brown x White

521
views