Pedigrees

Unit6.Lesson4-

Pedigrees

Pedigrees

● A graphic representation of an individual’s family

tree

● Used to recognize patterns of inheritance

Draw

Draw your family tree. Use Squares for Males and Circles for Females.

Pedigree Symbols

- male

- female

- half shade= carrier

- shaded= affected (have trait)

- unshaded = unaffected (do

NOT have trait)

Match

Match the following

• Square

• Circle

• Half Shaded

• Fully Shaded

• Unshaded

Male

Female

Carrier

Affected (have the trait)

Unaffected (do NOT have trait)

• Male

• Female

• Carrier

• Affected (have the trait)

• Unaffected (do NOT have trait)

Pedigree Symbols

- marriage

- offspring

Multiple Choice

How many Male offspring did the individuals in the 1st generation (2 people at the top) have?

• 4

• 6

• 2

• 3

Pedigree- Hemophilia in Europe’s

Royalty

Sex-Linked Recessive

6

Multiple Choice

What Chromosomes are Sex-Linked Traits on?

• X and Y

• Somatic

• Autosomal

• Genome

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

Open Ended

Why do affected fathers NEVER pass their X-linked recessive traits to their sons?

Multiple Choice

Which individual is a carrier in this pedigree?

• 1

• 2

• 3

• 4

Multiple Choice

Why are more males affected in sex-linked recessive pedigrees?

• Males have extra chromosomes

• Males do not have a second X Chromosome, which would allow for a masked recessive trait.

• Males have two X chromosomes, making them more vulnerable to recessive traits.

• Males do not have chromosomes

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

Open Ended

Why do sex-linked dominant pedigrees NOT have carriers?

Multiple Choice

Why do affected fathers pass the trait to ALL of their daughters in X-linked Dominant pedigrees?

• Affected Father only has one X to donate (and it is affected)

• Affected Father has 2 affected X chromosomes, doubling the chances for affected daughters.

• The daughters need two copies of X chromosomes, the father donates both.

• The trait is recessive and will always be expressed.

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

Multiple Choice

Why are males and females affected equally in autosomal recessive pedigrees?

• They are on the sex chromosomes, so they will be represented equally

• The traits are on chromosomes 1-22, males and females are the same for these chromosomes.

• It affects the X and Y chromosomes equally

• females have double the genetic material, allowing for equal distribution of alleles.

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

Multiple Choice

What type of inheritance is this

• Sex-Linked Recessive

• Sex-Linked Dominant

• Autosomal Recessive

• Autosomal Dominant

Multiple Choice

Which individual in the 3rd generation (III) must be a carrier?

• 1

• 2

• 3

• 5

Multiple Choice

What type of inheritance is this?

• Sex-Linked Recessive

• Sex-Linked Dominant

• Autosomal Recessive

• Autosomal Dominant

Multiple Choice

What type of inheritance is this?

• Sex-Linked Recessive

• Autosomal Recessive

• Sex-Linked Dominant

• Autosomal Dominant

Multiple Choice

What is the most likely type of inheritance seen in this pedigree?

• Sex-Linked Recessive?

• Sex-Linked Dominant

• Autosomal Dominant

• Autosomal Recessive

Match

Match the following:

Sex-Linked Recessive

Sex-Linked Dominant

Autosomal Recessive

Autosomal Dominant

• Sex-Linked Recessive

• Sex-Linked Dominant

• Autosomal Recessive

• Autosomal Dominant