Human cells normally have 46 chromosomes, based on 23 pairs – one from each parent. 22 of the pairs are called autosomes – they look the same in both males and females, while the 23rd pair (referred to as the sex chromosomes) differs between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome.
The animal with the fewest chromosomes is the Australian Jack Jumper Ant (Myrmecia pilosula) that has only one chromosome in the male of the species, while the female has two. When an organism has only a single set of chromosomes it is referred to as being “haploid” while organisms with two sets are “diploid.”
The mammal with the smallest number of chromosomes is the Indian muntjac (Muntiacus muntjak), a species of deer native to Southeast Asia in which the female has 7 and the male 6 chromosomes.