1. Color blindness: Can’t tell the difference between different colors.
2. Haemophilia: Delayed blood clotting at the wound site.
3. Dysplasia: Absence of sweat glands and teeth.
4. Spastic paraplegia: partial paralysis of muscles and irregular stiffness.
5. Ratkana : Sees something unclear at night.
6. Optic Atrophy: The optic nerve starts to deteriorate.
7. Juvenile glaucoma: Hardness of the eyeball
8. White Forelock: A bunch of white hair is seen at the front of the head.
9. Myopia: weak vision.
10. Muscular dystrophy: Muscular complications, the child’s mobility disappears at the age of 10 years.

1. Sex-linked traits are carried by the X chromosome, sometimes by the Y chromosome.
2. This gene is latent in most cases.
3. Sex-linked traits are more pronounced in males.
4. All sons of wives with the sex-linked trait will express the trait, but daughters will be carriers.
5. A father’s sex-linked traits are transmitted to daughters. This is called criss-cross inheritance.

Genes located on sex chromosomes are called sex genes. Traits controlled by sex chromosomes are called sex-linked traits. Intergenerational transmission of sex-linked traits through sex chromosomes is called sex-linked inheritance. Hereditary diseases transmitted from generation to generation through sex chromosomes are called sex-linked disorders or sex-linked abnormalities.

According to this system female is homogametic or XX and male has X chromosome and not Y. Females produce the same type of egg (X) and males produce two types of sperm (X and A). When a woman’s egg X meets a man’s sperm X, a female child (XX) will be produced. Again, the union of the woman’s egg X with the man’s sperm A will produce a son (XA). This method determines the sex of animals like grasshoppers, beetles, Orthoptera, Heteroptera, Dioscorea (plants).

According to this system female is homogametic or XX and male is heterogametic or XY. Females produce one type of egg (X) and males produce two types of sperm (X and Y). When a woman’s egg X meets a man’s sperm X, a female child (XX) will be produced. Again, the union of the woman’s egg X with the man’s sperm Y will produce a son (XY). This method determines the sex of animals such as humans, Drosophila, various insects, cannabis, cockroaches, Elodea etc.

The genetic process in which the sex of an organism is determined is called sex determination. Miss N. M. Stevell and Wilson proposed the theory of sex determination in insects after extensive research. According to this doctrine, the method of gender determination is sterile.

1. XX-XY System: According to this system female is homogametic or XX and male is heterogametic or XY. Females produce one type of egg (X) and males produce two types of sperm (X and Y). When a woman’s egg X meets a man’s sperm X, a female child (XX) will be produced. Again, the union of the woman’s egg X with the man’s sperm Y will produce a son (XY). This method determines the sex of animals such as humans, Drosophila, various insects, cannabis, cockroaches, Elodea etc.
2. XX-X0 System: According to this system female is homogametic or XX and male has X chromosome and not Y. Females produce the same type of egg (X) and males produce two types of sperm (X and A). When a woman’s egg X meets a man’s sperm X, a female child (XX) will be produced. Again, the union of the woman’s egg X with the man’s sperm A will produce a son (XA). This method determines the sex of animals like grasshoppers, beetles, Orthoptera, Heteroptera, Dioscorea (plants).

Animals that produce different types of gametes are called heterogametic sex. Male members are the heterogametic sex. Their gametes are called heterogametes.

Animals that produce the same type of gametes are called homogametic sex. Female members are the homogametic sex. Their gametes are called homogametes.

The chromosomes that determine the sex of an organism are called sex chromosomes. The 23rd chromosome in the human body is the sex chromosome. The two sex chromosomes are X and Y. It is called heterosome. A chromosome that does not play any role in determining the sex of an organism is called an autosome. Human body has 22 pairs of autosomes. Autosomes are identical XX. External differences are seen in male and female animals. This is called sexual dimorphism.

1. Presence of chromosomes: Chromosomes are always present in cells. If a cell is deficient in chromosomes, new cells produced from that cell will be deficient in chromosomes.
2. Pairing of Homologous Chromosomes: Homologous chromosomes are paired. That is, one small chromosome is linked to another small chromosome.
3. Independent Distribution of Chromosome Pairs: Chromosomes are arranged in pairs in organisms. Pairing is done independently.
4. Qualitative differences between chromosome pairs: Each chromosome contains genes controlling different traits. One chromosome causes normal cell growth and the other causes abnormal cell growth.
5. Sex determination: The sex of an organism is determined by sex chromosomes or allosomes.
6. Restoration: Fertilization restores the chromosome number in diploid cells.
7. Physical Basis of Heredity: Hereditary factors or genes are located on chromosomes. Hence it is called the physical basis of heredity.