Which two reproductive barriers are at play in mule reproduction?

A mule is produced when male donkey (jack) mates with a female horse (mare).

Explanation:1.Horse have 32 pairs of chromosomes while a donkey has only 31pairs. Hence, their offspring inherit 32 horse chromosomes and 31 donkey chromosomes leaving a chromosome that is not paired up this makes them infertile and inability to produce embryo.

2. Horse and donkey chromosomes are not similar unlike in human hence mules and can rarely produce the cells critical for reproduction i.e eggs and sperm.

The sun generates energy from a process called nuclear fusion. During nuclear fusion, the high pressure and temperature in the sun's core cause nuclei to separate from their electrons. Hydrogen nuclei fuse to form one helium atom.