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223 G enetiD isorder modified or defective gene. These diseases are inherited according to Mendel’s Laws. In some cases, the mutation can be spontaneous and where we will not get the previous family history. There may be single mutation in one gene causing specific disease like sickle cell anemia or multiple types of mutation in one gene and producing the same disease like cystic fibrosis (more than 200 different types mutation can occur in one gene). The single-gene or monogenic diseases can be classified into the following categories according to the inheritance pattern as follows: • Autosomal recessive Male • Autosomal dominant Female • X-linked recessive • X-linked dominant Affected individual For diagnosis of the inherited genetic disease mating one has to understand the concept of pedigree Offspring in birth order; analysis. The pedigree analysis is the process offspring numbered II-1 and II-2 of interpretation of information displayed as a family tree. If more than one person in a family Identical twins is involved with a disease then the pedigree Non-identical twins analysis can be done. Specific symbols are used to indicate different aspects of a pedigree Fig. 8.5: Symbols used in as shown in (Fig. 8.5). pedigree Autosomal recessive disorder The word ‘Recessive’ indicates that 2 copies of the genes are needed to have the trait and disorder in case of mutated gene. Out of the 2 copies one gene is inherited from father and one from mother. If an individual carries one defective recessive and one normal recessive gene then he or she will be the carrier and not develop the disease. On the basis of statistical projection it is estimated that every human being carries about 5 or more defective recessive genes which can cause a genetic disease. The disease phenotype of a recessive disorder is due to homozygosity of a recessive allele and the unaffected phenotype is secondary to corresponding dominant allele. This can be explained with the example of sickle cell anemia which is a autosomal recessive disease. Sickle cell disease is caused by a mutation in the hemoglobin-β gene found on chromosome 11. This results in a defective haemoglobin Reprint 2026-27