Pedigree Analysis - Practice Questions & MCQ

• Pedigree analysis is the process of determination of the exact mode of inheritance of a gene when sufficient family information is available.
• In the pedigree analysis, the inheritance of a particular trait is represented in the family tree over generations.
• In human genetics, the pedigree study provides a strong tool, which is utilized to trace the inheritance of a specific trait, abnormality or disease.
• Some of the important standard symbols used in the pedigree analysis have been shown below: 

Types of genetic disorders to be analyzed using pedigree charts:

• Autosomal disorder: A genetic disorder caused due to abnormality in autosomal chromosomes.
• X-chromosome linked disorder: A genetic disorder caused due to an abnormality in X-chromosome.
• Autosomal dominant disorder: A genetic disorder caused due to a dominant mutation in an autosomal chromosome. There are no carriers for autosomal dominant disorders.
• Autosomal recessive disorder: A genetic disorder caused due to a recessive mutation in an autosomal chromosome. An affected individual will have a pair of recessive alleles; single recessive allele would make an individual a carrier of the disease.
• X-linked dominant disorders: A genetic disorder caused due to a dominant mutation in an X-chromosome. It affects males and females equally.
• X-linked recessive disorders: A genetic disorder caused due to a recessive mutation in an X-chromosome. Males are affected by this type of disorder as they carry a single X-chromosome (said to be hemizygous for X-chromosome). Affected females will have both the X-chromosomes with recessive mutations. So, their chances of getting affected are reduced. Females are generally carriers for X-linked recessive disorders.
• Criss-cross inheritance: The pattern of inheritance of X-chromosome from fathers to daughters. Sons never receive their X-chromosomes from their father; Y-chromosome is inherited from father and X-chromosome from mother. Daughters receive one of the X-chromosomes from father and another one from mother.