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Standard operating procedure
Sketching Family Trees No: 015D
Family trees demonstrate the compilation of phenotypic records
of a family over several generations.
Research nurses trained in the method are responsible for sketching
all family trees (Pedigree chart/Genogram) from subjects.
trees should be constructed using the following symbols:-
the standard symbols to indicate persons, relationships and
significant details construct the family tree.
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.
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.
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
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.
to allocate each member a unique ID number. The family number
should be the same for all members of that family.
to check with the family that all their family details are
correct. Numbers CANNOT be changed after they have been allocated.
- 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.
(1987) Essential Genetics. Second edition. Blackwell Scientific