4.3
Nelson Biology 11
Selective Breeding
Pedigree Symbols
identical
twins
male
female
fraternal
twins (females)
mating
affected
individuals
Roman numerals
symbolize
generations.
I
II
1
2
known
heterozygotes
for autosomal
recessive
Arabic numbers symbolize
individuals within a given
generation.
3
Birth order within each group of offspring is drawn left to right,
oldest to youngest.
Sample Pedigree
I
1
2
II
1
2
3
4
5
III
1
2
3
Squares represent males and circles represent females. Individuals that express
the trait are shown in a coloured circle or square. If it is known, individuals that
carry the allele as part of a heterozygous genotype are shown by partial colour or
shading. A vertical line connects parents to offspring.
© Copyright 2002 Nelson Thomson Learning
Biology 11, page 142, Figure 4 27