Haemophilia is a hereditary genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding. This condition occurs due to a deficiency in specific clotting factors in the blood. As a result, individuals with haemophilia may experience prolonged bleeding following an injury, surgery, or even spontaneous internal bleeding, as their blood lacks the necessary components to form a stable clot effectively.

When an Rh-negative person is exposed to Rh-positive blood for the first time, the immune system begins to produce anti-Rh antibodies, a process called sensitization. Because this antibody production takes time, there is often no immediate, severe hemolytic reaction during the initial exposure, though the individual is then at risk for reactions upon subsequent exposures.

Colour blindness, particularly red-green colour blindness, is a classic example of an X-linked recessive genetic trait. It is passed from parents to offspring through mutations in genes located on the X chromosome. Because it is inherited, it is present from birth, unlike acquired conditions such as hepatitis (viral infection) or certain types of malignancies that may arise from environmental factors or somatic mutations.

Individuals with blood type AB possess both A and B antigens on their red blood cells but lack anti-A and anti-B antibodies in their plasma. Consequently, they are considered universal recipients within the ABO blood group system. They can safely receive red blood cells from donors with blood types A, B, AB, or O without triggering an immune reaction against the donor cells.

Diabetes mellitus is a metabolic disorder where the body cannot properly regulate blood glucose levels, often due to insufficient insulin production or cellular resistance. While type 1 diabetes has a strong genetic component, type 2 also shows hereditary patterns. This condition directly impacts how the body uses glucose for energy, distinguishing it from the other listed disorders which affect blood cells or immune function.

The Rh factor, or Rhesus factor, is an inherited protein found on the surface of red blood cells. It is a critical component of blood typing, alongside the ABO system. During a blood transfusion, it is essential to match the Rh status of the donor and the recipient to prevent an immune reaction, where the recipient's body attacks the donor blood, which can be life-threatening.

Colour blindness, particularly red-green colour blindness, is a classic example of an X-linked recessive genetic disorder. It is caused by mutations in genes located on the X chromosome, which affect the function of the cone cells in the retina responsible for detecting specific wavelengths of light.

Leukaemia is a type of cancer that affects the blood and bone marrow. It is clinically defined by the uncontrolled and malignant proliferation of leukocyte precursors, which leads to a significant and abnormal increase in the number of white blood cells (WBCs) circulating in the bloodstream. These immature or dysfunctional cells crowd out healthy blood cells, leading to various systemic complications.

The Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. Because it is a genetically determined trait passed down from parents to offspring, it is present in an individual's blood from the moment of conception and is detectable at birth. It does not develop later in life due to age or hormonal changes, making it a permanent blood group characteristic.

Colour blindness and haemophilia are classic examples of X-linked recessive genetic disorders. While sickle cell anaemia is autosomal, this grouping is often used in educational contexts to represent genetic conditions. The other options contain incorrect classifications, such as AIDS being viral rather than bacterial, or plague being bacterial rather than viral.