Each child receives 23 pairs of chromosome. Among them, 22 pairs of chromosome determine the physical characteristics of child whereas one pair determines the sex of the child. The chromosome which determines the sex of child is called sex chromosome. The sex chromosome of a father and mother is found in form X and Y. The sex chromosome of mother consists ‘X, X’ whereas the sex chromosome of father consists ‘X, Y’. During sexual contact, the sperm of male meet the ovum of female. At that time, if Y sex chromosome of male meets the X sex chromosome of female, then the birth of son takes place. Similarly, if X sex chromosome of male meet the X sex chromosome of female, then the birth of daughter takes place.
The life history of living organism starts with the division of fertilized ovum into many cells. Division of cell is governed by the hereditary bearer called gene. Then the fertilized cell goes on dividing and they are grouped to perform specific function. This group of cell is known as tissue. The tissues are grouped to perform definite work forming organ. When two or more than two organs group together and work in unison for the performance of definite function, system is formed. All the systems unite together and form up body. Thus, body is formed with the combination of various systems. The small unit called cell helps in the formation of a body.
0 comments:
Post a Comment