A child by the family from Thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby. (a) What is Thalassemia?
(b) How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.
(c) List the values your counseling can propagate in the families.(a) Thalassemia - is an autosomal recessive blood disease which can occur due to deletion of the genes controlling the formation of globin chains (commonly Alpha and Beta) of haemoglobin.
(b) Mother cannot be blamed for the disease as, it is an autosomal recessive blood disorder. The genes for the synthesis of globin chains are present on autosomes.
(i) Formation of Alpha chain is controlled by 2 genes present on chromosome 16 and
(ii) Formation of Beta-chain is controlled by one gene present on chromosome 11manifestation of the disease occurs when the progeny receives defective genes from both the parents (as thalassemia is expressed is homozygous recessive condition only).
(c) Values that can be propagated in families are
(i) One should be aware of such autosomal diseases and should get themselves checked for the same before marriage.
(ii) Manifestation of the disease occurs due to defective genetic set up of both the parent (so it is not only that the mother should be blamed.
(a) Why are thalassemia and haemophilia categorized as Mendelian disorders ? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.
(b) Write the genotypes of the normal parents producing a haemophilic son.
What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance?
Explain the genetic basis of blood grouping in human population.
(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?
