Pedigree Analysis - Genetic History of Family

Mendel’s works on the principle of inheritance in genetics remained a mystery for quite some time. Even though his works were not accepted during his era, later it was rediscovered and gained credibility. Currently, Mendel’s work is fundamental for studying inheritance pattern in living organisms. In addition, it helped to discover and predict how genetic disorders function. Let’s learn about pedigree analysis and how it helps in predicting genetic disorders.

What is Pedigree Analysis?

Mendel’s experiments revealed that the ‘factors’, what we know as genes, are responsible for the inheritance of traits. They are also accountable for the disorders prevailing in living organisms. Genes are the hereditary unit of organisms, responsible for structural and functional changes in them. Besides this, it is the cause of variation in organisms which can either result in a good or bad trait. The conclusions we derived were on the basis of controlled crosses on pea plants and other organisms. These controlled experiments can’t be performed in the human population due to ethical concerns. The only suggested solution to this limitation was pedigree analysis. I.e., to observe and analyze the pattern of inheritance in humans using their family history.

DNA sequences make up the genes of organisms which, in turn, encode for a particular protein. Any fluctuation in this sequence, for example –  mistakes during DNA transcription may lead to a change in the genetic codes or chromosomal aberrations. This can be transferred from parents to offspring. This inheritance of altered genes eventually causes genetic disorders in human beings. The Mendelian disorder is one of the types of genetic disorder in humans. These disorders arise from the change or alteration in a single gene. Their genetic inheritance is governed by the Mendelian genetics. They can be predicted based on the history of a family, with the help of a family tree. Mendelian disorders mostly occur in families with a certain pattern reflecting the change or alteration in a single gene. Their genetic inheritance is governed by the Mendelian genetics. Prediction of this disorder is based on the history of a family, with the help of a family tree. This process of analysis of a number of generations of a family is called the pedigree analysis. Pedigree analysis is a strong tool in human genetics which helps to predict the pattern of inheritance, even when data is limited.

A family tree can be picturized by a pedigree chart with all the members who are affected by genetic disorders.  In pedigree analysis, some standard symbols are used to distinguish different members of a family. A pedigree chart is given below:

Pedigree Analysis

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Practise This Question

Identify the correct statements related to phenylketonuria:

A. This disease is caused due to gene mutation

B. The affected individuals exhibit mental retardation and stunted growth

C. Pigmented patches are seen on the skin

D. Non-pigmented hair and eyes occur