PRINCIPLES OF HEREDITY.pptxprinciple

principles of heredity

1. PRINCIPLES OF HEREDITY

2. PRINCIPLE OF REPRODUCTION This asserts that “ like begets like ” meaning human produces human, animal produces animal. Children resemble their parents in some traits or their grandparents in some characteristics. Heredity produces similarities among those who belong to the same family.

3. PRINCIPLE OF VARIATION If heredity produces similarities, it also produces dissimilarities or variations. In a family even if there are many similarities yet there are some differences like complexion, shape of the face or body built. Variation also is seen in the color of the skin of say the Americans, the Asians, Europeans and Africans.

4. PRINCIPLE OF CHANCE Usually one egg ripens at ovulation period. Ovulation is the process of escape of one ripe ovum from the ovary to the fallopian tube. During the ovulation there are several thousands of spermatozoa tat enter the fallopian tube. As to which sperm fertilizes the ovum and produces combination of genes is a matter of chance.

5. PRINCIPLE OF DOMINANCE AND RECESSIVENESS It is said that characteristic traits are sure to appear in the children whenever they are present. These are the dominant traits. There are another characteristic traits that do not appear in children whenever the opposite traits are present. They show themselves only in the absence of the dominant traits. These are the recessive traits.

6. PRINCIPLE OF SEX-LINKED CHARACTERISTICS There are traits that are carried by the chromosomes which determine sex or genosomes and are only found in certain sex. Example of sex-linked characteristics are hemophilia and baldness. Sex linked characteristics are inherited only by male.