Pedigrees

Pedigrees

● A graphic representation of an individual’s family

tree

● Used to recognize patterns of inheritance

Pedigree Symbols

- male

- female

- half shade= carrier

- shaded= affected (have trait)

- unshaded = unaffected (do

NOT have trait)

Pedigree Symbols

- marriage

- offspring

Pedigree- Hemophilia in Europe’s

Royalty

Sex-Linked Recessive

6

X-linked Recessive

7

Look for:
• Trait is rare in pedigree
• Trait skips generations
• Affected fathers do NOT pass to their sons
• **Affected fathers pass to daughters (most daughters are carriers)
• **Males are more affected than females

Sex-Linked Dominant

9

Pedigree for X-linked Dominant

Look for:
• NO carriers
• Trait is common in

pedigree

• ***Affected fathers pass

to ALL of their
daughters

• Males and females are

equally likely to be
affected

XA?

XAa

XaYa

XAXa

Autosomal Recessive

11

Look for:
• Carriers (specifically

male carriers)

• Skips in generation
• Unaffected parents

(carriers) who have
affected children

• Affected person

must be
homozygous

• Males and females

affected equally

Autosomal Recessive

Autosomal Dominant

13

14

Autosomal dominant

● No carriers
● Males and

females
equally
affected

​Steps I use

1. Are there carriers, or does it skip a generation?
   Yes= Recessive No= Dominant

2. Is there equal representation between Males and Females?

   Yes= likely, Autosomal No= likely, Sex-Linked

3. Fathers pass the trait to ALL daughters?

   Yes= likely, Sex-linked Dominant No= Other