Pedigree Analysis

Pedigree Analysis
Pedigree Analysis is a tabular representation of a family history by taking a particular disease or character into consideration.

Proband or Propositus is an individual from which a pedigree is initiated.

Female are represented in circles. 

Male are represented in squares.


Individuals carrying the character to be studied are shaded.    


It helps us to find out whether the gene is dominant or recessive and autosomal or sex-linked. And the chances of expressing itself in the coming generations.

In the case of autosomal genes:
  • It equally affects both males and females.
In the case of sex-linked genes:
  • Affects the males as they are hemizygous.
  • The gene shows criss-cross inheritance i.e., the gene from the father is transferred to the grandson through the daughters.
  • In the case of a sex-linked dominant gene, more females are affected than males.
  • Never transferred from father to son.

In the case of dominant genes:
  • One or both the parents have the disorder.
  • It expresses itself in every generation.
  • The disorder is common in the pedigree.
  • The genotype is either homozygous (BB) or heterozygous (Bb).
  • It affects one-half of the children.
In the case of recessive genes:
  • Neither of the parents may have the disorder.
  • The disorder is rare in the pedigree.
  • Both parents are either heterozygous or homozygous recessive.
  • The disorder skips generations.
  • The genotype is always homozygous (bb).
  • Affected offspring are born to unaffected parents.


In the case of Holandric  ( Y-linked) genes:
  •  Affects the males only.
  • Father transfers it to son.
  • It never skips generations.
In the case of Cytoplasmic genes:
  • Gene is inherited from mother.
  • Affected mother transfers the gene to all its offspring.


Pedigree 1:

A sex-linked recessive character.

  • It mainly affects the males.
  • The gene skips generation.
  • Criss-cross inheritance is seen.

Pedigree 2:

It is an autosomal dominant character.

  • It affects male and female equally.
  • The gene expresses itself in each generation.

Pedigree 3:

It is an autosomal recessive character.

  • The gene skips generation.
  • Does not show criss-cross inheritance.

Pedigree 4:

It is a holandric gene.

  • As it affects only males.
  • The gene is transferred from father to son.

Pedigree 5:

It is a cytoplasmic gene.

  • Gene is inherited from the mother.
  • As it affects all the offsprings.


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