Genetic Disorders

Definition

Diseases caused by abnormalities in an individual's genes or chromosomes, which may be inherited from parents or arise from new mutations.

Key points

• Sickle cell anaemia and thalassaemia are inherited disorders of haemoglobin that cause abnormal or insufficient red blood cells; both are recessive and common in parts of India.
• Haemophilia is an X-linked recessive disorder in which blood does not clot properly; it mostly affects males and is famously called the royal disease.
• Colour blindness (red-green) is another X-linked recessive trait, far more common in men than women.
• Down syndrome is a chromosomal disorder caused by an extra copy of chromosome 21 (trisomy 21), not by a single faulty gene.
• Genetic disorders may be single-gene (sickle cell, haemophilia), chromosomal (Down syndrome), or multifactorial; carrier screening and genetic counselling help families assess risk.

Why it matters for CAPF

Sickle cell anaemia, thalassaemia, haemophilia and colour blindness as X-linked disorders, and Down syndrome as a chromosomal disorder are standard biology facts, and sickle cell control is a recognised national public-health programme.

Common confusion

Down syndrome is chromosomal (an extra chromosome 21), not a single-gene defect; haemophilia and colour blindness are X-linked and so are far more common in males. Sickle cell carriers (one copy) are usually healthy and may even resist malaria, while two copies cause the disease.

Related concepts

concept dna and rna, concept human blood groups, concept crispr

Parent note

biotechnology and genetics