Grayce P. Storey
When a child is born he usually possesses a gene pair for each trait. For any particular trait, one gene contributed by a parent is on one of the paired chromosomes. The other gene for that trait from the other parent is on the opposite chromosomes.
An offspring normally has 46 chromosomes or 23 pairs. Each parent contributes one of each chromosomes to make up the 46 chromosomes.
In the process of meiosis, sex cells are produced. These cells can be either sperm or egg cells. In this same process, the number of the chromosomes carried by each sex cell is exactly half the normal number of chromosomes found in the parent. In the formation of the offspring the sex cells combine and each contributes half the number of chromosomes. At the termination of the process the offspring gets the normal number of chromosomes and half are from each parent.
In 1907, Thomas Hunt, a zoologist, began his study of chromosomes and genetics by using the fruitfly. His study indicated a peculiarity about the chromosome shape. He labeled the pair with the rod-shape the X chromosome and the pair with the hook shape the Y chromosome. More studies and testing led to the outcome that the X and Y chromosome determine the sex of an organism. Any organism that has two (XX) chromosomes is a female and any organism that has one X and one Y chromosome is a male. This may be true in humans but in the case of the fruit fly, Drosophilia Melanogaster, the inheritance of sex depends on a simple chromosomal mechanism. The male species has one X chromosome and the female species has two (XX) chromosomes.
Meiosis Cell Division
(figure available in print form)