1. (a) Describe the disorder of sickle cell disease. Include a description of th
ID: 146597 • Letter: 1
Question
1. (a) Describe the disorder of sickle cell disease. Include a description of the molecular defect, inheritance, clinical features, diagnosis and treatment.
(b) Name another beta-globin mutation, and explain why this other mutation results in very different clinical features to sickle cell disease.
(c)A couple have three children. The first child has alpha-thalassemia trait, the second has Hb H disease whilst the third is unaffected. The mother, from Vietnam, has alpha thalassemia trait whilst the father has no symptoms. Outline the probable genotypes and phenotypes of the couple and their children, and predict whether this couple is at risk of conceiving a child with a severe form of alpha-thalassemia that is fatal in utero.
Explanation / Answer
a) It is a heriditary blood disease, dependent on autosomal recessive inheritence. So it is manifested only in those individuals who are homozygous recessive for the respective gene. In affected persons, the normal haemoglobin in the red blood cells(RBC)is entirely replaced by abnormal haemoglobin known as haemoglobin S. It has been shown that haemoglobin S differs from normal haemoglobin only in that the former contains the amino acid valine instead of glutamic acid at sixth position of it's two polypeptide chains. Such a 'mistake' is caused by a small mutation inthe DNA responsible for haemoglobin formation. But, it's effect on the functioning of the body is profound ie, haemoglobin S begins to crystallize when oxygen concentration falls. This causes the red blood cells, normally by concave disc shaped, to the shape of a sickle giving the disease tha name sickle cell anaemia. These cells inefficient in carrying oxygen. This disease which results is generally fatal. This disease caused by gene substitution.
Symptoms : the Victims suffers all the symptoms of oxygen shortage, weakness, emaciation, kidney and heart failure, etc.
Diagnosis : emergency medical treatment is necessary. A Blood test can check for haemoglobin S .
Treatment : Born marrow transplant and blood transfusions are the potential cure for this disease.
Good nutrition and hygiene is necessary.
b) Beta thalassemia is another beta - globin mutation. Mutations in the HBB gene cause beta thalassemia. In people, with this disease low level of haemoglobin lead to lack of oxygen in many parts of the body and shortage of RBC. Which can cause pale skin, weakness, fatigue and more complications. It increased risk of developing abnormal blood clots.
in thalassemia, both and globin chains can be affected but in sickle cell anaemia only the globin chains are affected. Which becomes apparent at 3-6 months after birth. It is caused by a gene deletion.
Community awareness on these diseases will help to decrease the incidence of them.
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