Mechanism of Heredity:- In the human body, there are certain germ cells, which are constituted out of innumerable genes. These genes are the real transmitters of heredity factors from one generation to the next. The genetic cell has a rodlike structure and is called the chromosom. It looks like a string or thread and it is the gene which passes, “a gene is the carrier of unit character of a heredity factor which is always transmitted as a unit in all or none fashion.” The chromosomes divide and subdivide like amoeba, increasing from two to four, four to eight and so on. These are referred to as the productive cells. The productive cells from the maternal side is called the ovum while the paternal productive cell is termed the sperm. The ovum and the sperm are cells which contain many pairs of genes. To be precise, the ovum and the sperm contain 23 genes each for the transmission of heredity traits. Some scientists hold the view that, instead of 23 genes each, these cells possess 24 cells each. Maternal and paternal genes union leads to the birth of children and it is this union which determines their heredity also.
HEREDITY.: Determining Process
1. Conception- The status of conception begins when the sperm from the father unites with the ovum from the mother.
2. Determination of sex- X and Y chromosomes play the main role in determining the sex of the child. The father possesses both X and Y chromosomes whereas the mother possesses only the X chromosome. When they divide and subdivide, it possesses 23 pair of chromosomes. They are equal in number.
3. Twins- Among human beings only some women are found to possess a tendency to give birth to twins or those bom of the same ovum and non-identical. The latter kind is by far the more numerous.
Identical twins- one fertilized ovum is devided into two separate parts then two separate foetus grow. Both are same sex.
Non Identical twins - Twins when two ovum become mature by two sperms may be of the same sex, as of different sex.
2. Determination of sex- X and Y chromosomes play the main role in determining the sex of the child. The father possesses both X and Y chromosomes whereas the mother possesses only the X chromosome. When they divide and subdivide, it possesses 23 pair of chromosomes. They are equal in number.
3. Twins- Among human beings only some women are found to possess a tendency to give birth to twins or those bom of the same ovum and non-identical. The latter kind is by far the more numerous.
Identical twins- one fertilized ovum is devided into two separate parts then two separate foetus grow. Both are same sex.
Non Identical twins - Twins when two ovum become mature by two sperms may be of the same sex, as of different sex.
