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Chapter 4: Problem 24

Horses can be cremello (a light cream color), chestnut (a reddish brown color), or palomino (a golden color with white in the horse's tail and mane). Of these phenotypes, only palominos never breed true. The following results have been observed: cremello \(\times\) palomino \(\longrightarrow 1 / 2\) cremello \(1 / 2\) palomino chestnut \(\times\) palomino \(\longrightarrow 1 / 2\) chestnut \(1 / 2\) palomino palomino \(\times\) palomino \(\longrightarrow 1 / 4\) chestnut \(1 / 2\) palomino \(1 / 4\) cremello (a) From these results, determine the mode of inheritance by assigning sene symbols and indicating which genotypes yield which phenotypes. (b) Predict the \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) results of many initial matings between cremello and chestnut horses.

Short Answer

Expert verified
Answer: The genotypes for the horse coat color phenotypes are Cremello (CC), Chestnut (cc), and Palomino (Cc). When a cremello horse (CC) mates with a chestnut horse (cc), the F1 generation will be all Palomino (Cc). When the F1 Palomino horses mate, the F2 generation will have 1/4 Cremello (CC), 1/2 Palomino (Cc), and 1/4 Chestnut (cc).

Step by step solution

01

1. Assigning gene symbols to different horse color phenotypes

We can use the letter C for the gene that controls the horse coat color. Let's represent the alleles responsible for cremello, chestnut, and palomino coat colors as CC, cc, and Cc, respectively.
02

2. Finding the genotypes and inheritance patterns from given results

We can analyze each possible cross to understand the gene inheritance pattern: - Cremello × Palomino: (CC) × (Cc) → 1/2 Cremello (CC) + 1/2 Palomino (Cc) - Chestnut × Palomino: (cc) × (Cc) → 1/2 Chestnut (cc) + 1/2 Palomino (Cc) - Palomino × Palomino: (Cc) × (Cc) → 1/4 Chestnut (cc) + 1/2 Palomino (Cc) + 1/4 Cremello (CC) From the above crosses, we can say that the genotype of the Cremello is homozygous dominant (CC), Chestnut is homozygous recessive (cc), and Palomino is heterozygous (Cc). (b)
03

1. Predicting F1 generation

To predict the F1 generation from the initial matings between cremello (CC) and chestnut (cc) horses, we can perform a Punnett square between CC and cc: | | C | C | |---|---|---| | c | Cc | Cc | | c | Cc | Cc | All F1 offspring will be heterozygous (Cc) and exhibit the palomino phenotype.
04

2. Predicting F2 generation

From the result in the F1 prediction, we know the F1 offspring have a Cc genotype. To predict the F2 generation, we can perform a Punnett square of the F1 offspring between Cc and Cc: | | C | c | |---|---|---| | C | CC | Cc | | c | Cc | cc | The F2 generation will have the following distribution of genotypes and phenotypes: - 1/4 Cremello (CC) - 1/2 Palomino (Cc) - 1/4 Chestnut (cc)

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Most popular questions from this chapter

In humans, the ABO blood type is under the control of autosomal multiple alleles. Red-green color blindness is a recessive X-linked trait. If two parents who are both type A and have normal vision produce a son who is color- blind and type \(0,\) what is the probability that their next child will be a female who has normal vision and is type \(0 ?\)

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