People wit sickle-cell anaemia have haemoglobin

This question is asking about the type of haemoglobin that people with sickle-cell anaemia have and their genetic makeup. Sickle-cell anaemia is a genetic disorder that affects the red blood cells in the body. In normal individuals, haemoglobin A is present which helps red blood cells to carry oxygen throughout the body. However, in individuals with sickle-cell anaemia, haemoglobin S is present instead of haemoglobin A.

The question is asking us to identify the correct option that explains the genetic makeup of individuals with sickle-cell anaemia. The correct answer is Option A, which states that individuals with sickle-cell anaemia have haemoglobin S and are homozygous recessive. Homozygous means that they have two copies of the same gene, and recessive means that the gene is only expressed when both copies are present.

In simpler terms, this means that individuals with sickle-cell anaemia inherit two copies of the sickle-cell gene, one from each parent. Both copies are the same, which means that they are homozygous for the sickle-cell gene. This is why they produce haemoglobin S, which causes their red blood cells to become sickle-shaped and can cause various health problems.

Option B, C, and D are incorrect because they describe individuals who are carriers of the sickle-cell gene but do not have sickle-cell anaemia themselves. These individuals have one copy of the sickle-cell gene and one copy of the normal gene, which makes them heterozygous for the sickle-cell gene. This means that they do not have sickle-cell anaemia but can pass the gene on to their children.

In summary, people with sickle-cell anaemia have haemoglobin S and are homozygous recessive, which means they have two copies of the sickle-cell gene. Carriers of the sickle-cell gene are heterozygous and have one copy of the sickle-cell gene and one copy of the normal gene.