Constructing a Pedigree
pedigree is a special chart or family tree that uses a particular set of
standardized symbols. Pedigrees are used to show the history of inherited traits
through a family. In a pedigree, males are represented by squares
and females by circles
. An individual who
exhibits the trait in question, for example, someone who suffers from
hemophilia, is represented by a filled symbol
. A horizontal line
between two symbols represents a mating
. The offspring are
connected to each other by a horizontal line above the symbols and to the
parents by vertical lines. Roman numerals (I, II, III, etc.) symbolize
generations. Arabic numerals (1,2,3, etc.) symbolize birth order within each
generation. In this way, any individual within the pedigree can be identified by
the combination of two numbers (i.e., individual II3).
Inherited traits can be traced through a
familyís history by constructing a pedigree chart.
Large sheet of paper or poster board
Examine Figure 1 that traces the
ability to roll your tongue through three generations in a family. Remember:
Blackened circles show the trait and circles are females and squares are
Determine which parents and which
offspring would be able to roll their tongue.
the Passage 1 about the Smith family and their inherited trait of dimples.
reading the passage, construct a pedigree showing all family members in each
generation that does and does NOT have dimples.
the pedigree is constructed, write the correct genotype by each person in the
Grandfather and Grandmother Smith smiled a lot and showed off their
dimples each time. They had a son named John, who had dimples, and daughter
named Julie, who did not. Julie died at an early age, but her brother John Smith
met and married Mary Jones because she had the most beautiful dimples when she
smiled. They had 5
children, 2 boys and 3
girls. Only one of their sons, Tom,
had dimples, but both girls, Judy and Kay, had dimpled smiles. Their sister June
lacked dimples. After college, Tom met and married Jane Kennedy who also had
dimples. They had 3 children, all girls, who shared their parentís dimpled
smile. Tomís sister Kay married a lawyer named James who seldom smiled and
didnít have dimples. Their only son Matthew was like his mother when he
smiled. Judy never married. Tomís sister, June, married a doctor and had 5
children. Three of the children were boys, Jay, Fred, and Mike. Mike and Fred
had dimples like dad, but Jayís smile was like his momís lacking dimples.
One sister, Susan, had dimples, but the other, Katherine, didnít.
type of information does a pedigree contain?
do you show the presence of a trait in a pedigree?
do you denote males & females in a pedigree?
your pedigree, is the presence of dimples a dominant or recessive trait?
could examining a family pedigree be helpful to a couple wanting to have