There are almost as many different types of four-wheel-drive systems as there are four-wheel-drive vehicles. It seems that every manufacturer has several different schemes for providing power to all of the wheels.
Most mammals have only one pair of sex chromosomes in each cell. Males have one Y chromosome and one X chromosome, while females have two X chromosomes. In mammals, the Y chromosome contains a gene, SRY, which triggers embryonic development as a male. The Y chromosomes of humans and other mammals also contain other genes needed for normal sperm production.
Sources: Biology Student. Depending on the type of karyotype, you can tell what type of organism it is, if it has 23 pairs then you would know it is a human because humans have 46 chromosomes, one half from your mom and one half from your dad, making 23 pairs.