Question

A horse has 64 chromosomes and a donkey has 62, Mules result from crossing a horse and donkey. Which of the following statements is correct?
A. Mules can have either 64, 63 or 62 chromosomes.
B. Mules are infertile.
C. Mules have well defined gender(male/female).
D. Mules have 63 chromosomes.

Answer 1

Hint: A donkey is the half of a male donkey and a half female horse. Since horses and donkeys are different species, they don't have the capacity to reproduce.

Complete Answer:
- Mules are a hybrid of two species – a female horse and a male donkey, so they end up with an odd number of chromosomes. A horse has 64 chromosomes and a donkey has 62. A mule inherits 63. An even number of chromosomes is needed to divide into pairs and reproduce.
- To understand why this, we need to understand how sperm and eggs are made, we have two copies of each of our chromosomes, one from mom and one from dad. This means we have two copies of chromosome 1, two copies of chromosome 2, etc. However, this isn't entirely true for the mules.
- Horses have 32 pairs of chromosomes while a donkey has only 31. As a result, their offspring will inherit 32 horse chromosomes and 31 donkey chromosomes, which leaves one chromosome that can’t match with anything. In mules, this extra chromosome poses a problem when it comes to creating sex cells. But an extra chromosome is not the only problem
- A mule’s cells can divide and make new cells just fine but chromosomes sort differently in regular cells than they do in sperm and egg. Instead of matching up, they just sort into two new cells. So, for the mule, each cell ends up with 63 chromosomes. Nothing on the extra or missing chromosome causes it any harm.

Therefore, the correct answer for this question is D, i.e. Mules have 63 chromosomes.

Note: Horse and donkey chromosomes are so dissimilar that mules rarely can produce the cells critical for reproduction which are eggs and sperm.