Which of the following is a characteristic symptom of haemophilia, a hereditary blood disorder?

Introduction / Context:
Haemophilia is a well known hereditary disease related to blood clotting. Understanding its main symptom is important in biology, medicine, and general awareness. This question checks whether you can correctly identify the hallmark feature of haemophilia among various symptoms associated with other conditions.

Given Data / Assumptions:

• The disease mentioned is haemophilia.
• The options include night blindness, no clotting of blood, rickets, and loss of haemoglobin.
• We assume basic knowledge of common nutritional and genetic disorders.

Concept / Approach:
Haemophilia is an X linked genetic disorder where certain clotting factors in blood are absent or defective. As a result, the blood of an affected person does not clot properly, leading to prolonged bleeding even after minor injuries. Night blindness is due to vitamin A deficiency, rickets results from vitamin D deficiency, and loss of haemoglobin relates more to anaemia. The correct approach is to match haemophilia with defective blood clotting and persistent bleeding.

Step-by-Step Solution:
Step 1: Recall that haemophilia affects the blood clotting system due to deficiency of clotting factors. Step 2: Understand that people with haemophilia bleed for a longer time after cuts and may have internal bleeding in joints and muscles. Step 3: Recognize that the key symptom is delayed or absent formation of a stable blood clot. Step 4: Note that night blindness is associated with vitamin A deficiency and affects vision in low light, not clotting. Step 5: Remember that rickets is a bone disorder due to vitamin D deficiency, characterized by soft bones and deformities. Step 6: Understand that loss of haemoglobin is a feature of anaemia, which leads to fatigue and pallor, not characteristic prolonged bleeding. Step 7: Therefore, the option that directly describes haemophilia is no clotting of blood.
Verification / Alternative check:
Medical descriptions of haemophilia emphasize prolonged bleeding time, frequent nosebleeds, bleeding gums, and internal joint bleeding after minor injuries. Laboratory tests show deficiencies in specific clotting factors. There is no primary mention of night blindness, rickets, or severe haemoglobin loss as defining features. Cross checking with common associations of vitamin deficiencies shows that night blindness and rickets belong to other nutritional disorders, and anaemia corresponds to haemoglobin problems. This confirms that defective clotting is the central symptom of haemophilia.

Why Other Options Are Wrong:
Night blindness: Caused mostly by vitamin A deficiency and characterized by poor vision in dim light, unrelated to clotting factors.
Rickets: Results from vitamin D deficiency and leads to bone deformities in children, not bleeding disorders.
Loss of haemoglobin: This condition leads to anaemia and reduced oxygen carrying capacity, which is separate from haemophilia.

Common Pitfalls:
Students sometimes confuse various deficiency diseases when memorizing them quickly. Mixing up haemophilia with anaemia is particularly common because both involve blood. To avoid confusion, remember that haemophilia is associated with clotting factors and bleeding, while anaemia relates to haemoglobin and oxygen transport. Using simple mental links like haemophilia and haemorrhage both beginning with similar sounds can help recall that it is a bleeding disorder.

Final Answer:
A characteristic symptom of haemophilia is No clotting of blood, leading to prolonged bleeding even after minor injuries.