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Nursing and Scientific Teams

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Standard operating procedure

Sketching Family Trees No: 015D

1. Introduction

Family trees demonstrate the compilation of phenotypic records of a family over several generations.

2. Responsibilities

Research nurses trained in the method are responsible for sketching all family trees (Pedigree chart/Genogram) from subjects.

3. Equipment

  • None

4. Method

All family trees should be constructed using the following symbols:-

  • Using the standard symbols to indicate persons, relationships and significant details construct the family tree.

  • Construction of the family tree, for this study, will start from the Index (proband) case. The rest of the nuclear (immediate) family should be constructed around this individual. This means the Index or proband maybe a parent or a sibling in any order.

  • When constructing the family tree, fathers are always number 1 and on the left hand side of a marriage pair. Mothers are always number 2 and on the right. Siblings always start from number 3 onwards and the eldest always starts on the left hand side. The remaining siblings are chronologically arranged, oldest to youngest. For example see figure 1.

    Figure 1

  • The oldest first rule applies to siblings only. With parents, fathers are always number 1 and mothers are always 2.

  • If the family contains a death or second marriage they are drawn on the family tree as demonstrated in figure 2. Starting with the new parent, they are given a number as shown in figure 2. The number allocated to these individuals is the next available number after that of the last sibling of the original nuclear family.

    Figure 2

  • Construct the family tree with a member of the family, in order that they can verify the positions of all their family members. Ensure to include all family members, including those which may have died.
  • Ensure to allocate each member a unique ID number. The family number should be the same for all members of that family.
  • Ensure to check with the family that all their family details are correct. Numbers CANNOT be changed after they have been allocated.

5. Additional Information

  • If you are unsure how to draw a family tree or allocate a number to a family seek advise from either the Nurse or Medical Co-ordinator.
6. Reference Documents

Russell.P.J. (1987) Essential Genetics. Second edition. Blackwell Scientific Publications, Oxford.



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