In pedigree

Square represents male blackened square or circle represents affected individual.

Horizontal line represents-parents

The study of inheritance of genetic traits in several generations of a human family in the form of a family tree diagram is called pedigree analysis.

Advantages

$(i)$ It helps in genetic counselling to avoid disorders

$(ii)$ It shows the origin of a trait and flow of a trait in a family

$(iii)$ It is important to know the possibility of a recessive allele that can cause genetic disorders like colour blindness, haemophilia, etc.

Signosed in the pedigree are