Question

Pick out the correct statements.
(a) Haemophilia is a sex-linked recessive disease.
(b) Down’s syndrome is due to aneuploidy.
(c) Phenylketonuria is an autosomal recessive gene disorder.
(d) Sickle cell anemia is an X-linked recessive gene disorder.

A. (a) and (d) are correct.
B. (b) and (d) are correct.
C. (a), (c) and (d) are correct.
D. (a), (b) and (c) are correct.

Answer 1

Hint: Haemophilia, Down’s syndrome, Phenylketonuria and Sickle cell anaemia all are the genetic disorders. The genetic disorder passed from the parents to the offsprings. These disorders are caused by the single gene mutation, many gene mutations and chromosomal mutation.

Complete Answer:
A. Haemophilia: Haemophilia is a sex-linked recessive disorder. It is also called a bleeder's disease because in this disease the affected person is unable to form blood clots and bleeds continuously even on a small cut or injury.
There are two types of haemophilia-
1. Haemophilia A – Haemophilia A is caused by the low amount of clotting factor VIII.
2. Haemophilia B – Haemophilia B is caused by the low amount of the clotting Factor IX.

Symptoms of Haemophilia:
- External and internal bleeding
- Joint pain and welling
- Blood in stools or urine

B. Down’s syndrome: Trisomy of chromosome 21 caused due to the abnormal cell division. Trisomy of chromosome 21 means that the 21th chromosome has an extra copy of chromosome 21. There is no cure for Down’s syndrome, the disabilities are life long. However people with Down’s syndrome can live healthy lives but their mental and physical development delays. This syndrome is caused due to the aneuploidy or trisomy which is the addition of an extra chromosome.

Symptoms of Down’s syndrome:
- Flat facial features
- Small head and ears
- Short neck
- Bulging tongue
- Poor muscle tone
- Impulsive behavior
- Poor judgement
- Mild to moderate intellectual disability.

C. Phenylketonuria: Phenylketonuria is an autosomal recessive gene disorder which is caused by mutations in both alleles of the gene for PAH(Phenylalanine hydroxylase) found in chromosome 12. The enzyme Phenylalanine hydroxylase is used to convert phenylalanine into tyrosine, which the body uses to create neurotransmitters such as epinephrine, norepinephrine and dopamine. When this enzyme is missing from the body phenylalanine accumulated in the body.

Symptoms of Phenylketonuria:
- Tremors, trembling or shaking
- Stunted growth
- Hyperactivity
- Skin conditions such as eczema
- Brain damage

D. Sickle cell anemia: Sickle cell anemia is an autosomal recessive disorder. In this disease the shape of RBC changes from biconcave to sickle like shape. Due to the sickle shape of RBCs they cannot easily pass through the veins. They get stuck at the branching points in the vein. This disease is caused by the point gene mutation in the Beta-globin chain at 6th position.

Symptoms of Sickle cell anemia:
- Attacks of pains
- Anaemia
- Swelling in the hands and feet
- Bacterial infections
- Stroke

Hence, option D is the correct answer for this question.

Note: In haemophilia patients can lose a large amount of blood even on a small injury. If a patient didn’t get a proper treatment then bleeding can cause the death of a patient.