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.
Human Male Chromosomes. In the normal karyotype of male chromosomes, 23 pairs of very long DNA molecules and their associated proteins carry the hereditary information of a man.
A normal human cell should contain exactly 46 chromosomes. They are matched into 23 pairs. Pairs one through 22 are numbered by size and appearance, and are the same in males and females. The 23rd pair is referred to as the sex chromosomes. Typically, females have 2 X chromosomes, while males have an X and a Y.