Which of the following most appropriately describes haemophilia? (A) X-linked recessive gene disorder (B) Chromosomal disorder (C) Dominant gene disorder (D) Recessive gene disorder

Options

A. X-linked recessive gene disorder
B. chromosomal disorder
C. Dominant gene disorder
D. Recessive gene disorder

Answer

To determine which option most appropriately describes hemophilia, let's analyze the characteristics of the disorder step by step.

### Step 1: Understand Hemophilia
Hemophilia is primarily known as a blood clotting disorder. Individuals with hemophilia have difficulty forming blood clots, which can lead to excessive bleeding.

**Hint:** Remember that hemophilia is related to blood clotting and is a genetic condition.

### Step 2: Identify the Genetic Basis
Hemophilia is caused by a mutation in genes that are responsible for producing clotting factors. The most common types of hemophilia are Hemophilia A and Hemophilia B, both of which are linked to specific genes located on the X chromosome.

**Hint:** Focus on the location of the genes responsible for hemophilia; they are found on the X chromosome.

### Step 3: Determine the Mode of Inheritance
Since hemophilia is linked to the X chromosome, it follows an X-linked inheritance pattern. This means that the disorder is passed down through the X chromosome, and males (who have one X and one Y chromosome) are more likely to express the disorder than females (who have two X chromosomes).

**Hint:** Consider how the X chromosome is inherited differently in males and females.

### Step 4: Classify the Disorder
Hemophilia is classified as a recessive disorder because a person must inherit two copies of the mutated gene (one from each parent) to express the disorder. However, since males have only one X chromosome, they will express hemophilia if they inherit a single mutated gene on their X chromosome.

**Hint:** Recall that recessive disorders require two copies in females but only one in males.

### Step 5: Evaluate the Options
Now, let's evaluate the provided options:
- (A) X-linked recessive gene disorder: This is correct because hemophilia is indeed linked to the X chromosome and is recessive.
- (B) Chromosomal disorder: This is incorrect as hemophilia is not caused by abnormalities in the number or structure of chromosomes.
- (C) Dominant gene disorder: This is incorrect because hemophilia does not follow a dominant inheritance pattern.
- (D) Recessive gene disorder: While hemophilia is recessive, this option does not specify that it is X-linked, which is crucial.

### Conclusion
The most appropriate description of hemophilia is (A) X-linked recessive gene disorder.

**Final Answer:** (A) X-linked recessive gene disorder

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