A horse (2n = 64) and a donkey (2n = 62) can mate and produce a mule. How many chromosomes would there be in a mule's body cells?
a. 31
b. 62
c. 63
d. 126

Verified step by step guidance

1. Step 1: Understand the chromosome numbers of the parents. The horse has a diploid chromosome number of 64 (2n = 64), and the donkey has a diploid chromosome number of 62 (2n = 62).
2. Step 2: Recall that during sexual reproduction, each parent contributes half of their chromosomes to the offspring. This means the horse will contribute 32 chromosomes (n = 64 / 2), and the donkey will contribute 31 chromosomes (n = 62 / 2).
3. Step 3: Add the haploid contributions from both parents to determine the total number of chromosomes in the mule. Use the formula: \( \text{Total chromosomes} = \text{Horse contribution} + \text{Donkey contribution} \).
4. Step 4: Recognize that the mule inherits one set of chromosomes from each parent, resulting in a hybrid chromosome count. This hybrid count is the sum of the haploid contributions from the horse and donkey.
5. Step 5: Verify that the mule's chromosome count represents the total number of chromosomes in its body cells, which are diploid (2n). This is because body cells contain the full set of chromosomes inherited from both parents.

Key Concepts

Chromosome Number

Chromosome number refers to the total count of chromosomes in a cell. In diploid organisms, this number is represented as 2n, where n is the number of pairs of chromosomes. For horses, the diploid number is 64 (2n = 64), and for donkeys, it is 62 (2n = 62). Understanding the chromosome number is essential for determining the genetic makeup of hybrid offspring.

Hybrid Offspring

Hybrid offspring are the result of mating between two different species or breeds, leading to a combination of genetic material from both parents. In this case, a mule is a hybrid resulting from the mating of a horse and a donkey. Hybrids often have an intermediate number of chromosomes, which can affect their fertility and other biological traits.

Chromosome Inheritance in Hybrids

In hybrids like mules, the chromosome count is typically the average of the two parent species, but it may not be a whole number. Mules inherit 32 chromosomes from the horse and 31 from the donkey, resulting in a total of 63 chromosomes (2n = 63). This unique chromosome number is significant as it often leads to sterility in hybrids due to mismatched chromosome pairing during meiosis.