Rules Regarding Recording a Pedigree | Genetics

In this article we will discuss about the rules regarding the recording a pedigree.

A detailed health history of the family is the basic prerequisite for any form of genetic counselling and it is essential to have detailed information about the patient’s (supposed to have any genetic abnormality or disease) relatives.

A detailed pedigree gives us the necessary basic information for all further genetic considerations. It simplifies matters for oneself and the potentially required geneticist if the pedigree is drawn up with the symbols in common usage which are:

1. Record must show all the children of a sib ship, whether it is defective or normal.

2. Sex of the Children.

3. A pedigree is supposed to show the various births in their proper order.

4. If for some reason, recorded order differs from the actual and known order, then this must be pointed out.

5. It is also very important to try to locate still births and miscarriages in a sib ship as correctly as possible.

6. It is desirable to arrange the pedigree with the paternal line on the left hand side and the maternal line on the right hand side.

7. In numbering the pedigree to indicate successive generations with Roman numerals (descending order) and to indicate the order within the generation with Arabic numerals (from left to right).

8. It is particularly important to keep a separate list containing the most important data as following:

(a) The number within the pedigree.

(b) Family name, first name and middle name (if any).

(c) Date and place of birth and also date of death.

(d) Address.

(e) Name of the patient’s doctor and hospital with address.

(f) A brief medical case history of the patient.

(g) Specific nature of inquiry.

(h) Family members known to be unaffected.

9. All the information gathered should be verified and expanded or qualified by questioning all the known members of the family.

10. Sources of information are best recorded as well.

11. Information concerning the past generations or distant relatives should be or must be taken from the grandmother.

12. Information concerning marriage partners should preferably be written by both.

Apart from the above rules, individual whose specific condition is important to the outcome of the genetic evaluation should be medically examined. If that proves impossible, the patient’s own doctor(s) should be questioned for the relevant data.

How far back is one required to go for recording a pedigree?

It depends upon:

1. The kind of genetic defect that confronts us.

2. Which mode of inheritance applies (i.e. Dominant, Recessive, Mendelian, Multiple factorial, Sex-linked, Autosomal etc.)?

3. How definitely the mode of inheritance has been ascertained?

4. Existence of any blood relationship between the families of the married couples.