Q. 164.4( 20 Votes )
Mention any two a
Sickle cell anaemia: This is an autosomal linked recessive trait that can be transmitted from parents to offsprings only when both the parents are the carrier for the gene governing the trait. Thus only homozygous recessive individuals show the diseased phenotype. This defect is caused by the substitution of the amino acid Glutamic acid by Valine at the sixth position of the β globin chain of the haemoglobin molecule.
Symptoms: The different symptoms of sickle cell anaemia are- rapid heart rate, breathlessness, weakness, excessive thirst, chest pain, prone to diseases such as jaundice, delayed growth and puberty and decreased fertility.
Down’s Syndrome: It was first discovered and published in 1866 by a British physician John Langdon Brown. This is a trisomic condition of chromosome 21 where an extra copy of chromosome 21 is found. It is the result of asymmetrical division in meiosis of the parents.
Symptoms: They are characteristically short; have protruding, furrowed tongue; short and broad hands with fingers showing characteristic palm and fingerprint patterns. Physical psychomotor and mental development is retarded and poor muscle tone is characteristic. Children affected by Down’s syndrome are prone to respiratory diseases and heart malfunctions and they show incidence of leukemia approximately 20 times higher than the normal population. Its estimated occurrence is approximately 1 in every 800 live births.
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