Proband: Definition & Overview

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

What - or who - is a proband? Read this lesson to find out what a proband is and why a proband is important for treating genetic disorders. Then take the quiz to test what you've learned.

What is a Proband?

Katie and John have their first baby together - a little boy named Caleb. Much to their surprise, Caleb is born with cystic fibrosis and is the first person in either of their families to have this condition. What does this mean? Well, Caleb is their proband.

A proband isn't so much a 'what' as a 'who.' Specifically, it is the first person in a family who is treated for a genetic disorder. Even if other family members have the condition, the proband is the family member who is being treated and is like the 'patient zero,' bringing the condition to light. Caleb is now the proband of Katie and John's family, and they have learned they are carriers of genes that may combine to develop future children with cystic fibrosis.

Once one person in a family is diagnosed with a genetic disorder, other members of the family can begin screening to see if they too are affected or are potential carriers. In some cases, the term proband will not refer to the first diagnosed person; rather it will refer to the ancestor first known to have the disorder as well, but this is a less-common definition. For the purposes of this lesson, a proband will refer to the first person diagnosed with the disorder who is seeking treatment. Male and female probands have different terms, with a male being the 'proposito' or 'propositus' and a female being a 'proposita.'

In this example, Grandma is the proband of the family. She is outlined in red, indicating where a genetic disorder was first identified.
proband example

Probands can begin undergoing treatment and testing for their disease, which can then be used to help treat future family members who may carry the genetic combination creating the disorder. Tracking medical ailments throughout a family tree can also help identify possible genetic disorders lurking in that family's gene pool. Tracking different traits throughout a family is called developing a family pedigree, and this is one of the most effective ways to identify the presence of disorders.

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