Download Pedigrees

What is a pedigree?
Pedigree: family history - shows how a trait is
passed on through generations
a graphic representation of a family tree
Pedigree can tell you if a trait is passed on
genetically and if the alleles are dominant or
recessive
How do you read a Pedigree?
Generation
Generation
And
Individual
(III-1)
Individual
Analyze the Pedigrees
In your group, analyze the 4 pedigrees in your IN
 Who’s affected?
 Every generation affected?
 How many males/females affected?
 Are there any carriers?
 Is the trait dominant or recessive?
What are the four types of pedigrees?
AUTOSOMAL DOMINANT
***Found in
genes on
chromosomes
1-22***
 Who will express the trait more often... Males or Females?
They are equally likely to have the trait
 Does the trait occur every generation or skip generations?
Occurs every generation
 Which genotypes express the trait?
Homozygous Dominant or Heterozygous
AUTOSOMAL DOMINANT
What’s the
genotype for:
• Individual I-1
aa
•Individual I-2
Aa
***Use A or a for alleles***
•Individual II-7
Aa
Autosomal Dominant Disorder
Neurofibromatosis
AUTOSOMAL RECESSIVE
***Found in
genes on
chromosomes
1-22***
 Who will express the trait more often... Males or Females?
They are equally likely to have the trait
 Does the trait occur every generation or skip generations?
Skips generations
 Which genotypes express the trait?
Homozygous Recessive
 If parents without the trait have children with the trait, what must be the
genotype of both parents?
Heterozygous
 If a Parent has the trait, their offspring who do not have the trait must have
what genotype?
Heterozygous
AUTOSOMAL RECESSIVE
What’s the genotype for:
Individual I-2
Aa
Individual II-3
aa
***Use A or a for alleles***
Individual III-2
AA or Aa
Autosomal Recessive Disorder
Albinism
SEX-LINKED DOMINANT
***Found in
genes on the X
chromosome***
Will all daughters of males with the trait inherit the trait?
YES!...Why?
Can males pass the trait on to their sons?
NO!
Will all daughters and sons of females with the trait inherit the trait?
Depends on the mother’s genotype
SEX-LINKED DOMINANT
What’s the genotype
for:
Individual I-1
XHy
Individual II-3
Xhy
Individual II-4
XHXh
***Use XH, Xh, and y for alleles***
Sex-Linked Dominant Disorder
Rickets
SEX-LINKED RECESSIVE
***Found in
genes on the X
chromosome***
Is the trait more common in Males than Females? Why?
Males
If a Male has the trait what will be genotype of his daughters?
Heterozygous (Carriers)
What is the chance that a son of a female carrier will inherit the trait?
50%
SEX-LINKED RECESSIVE
What’s the genotype for:
Individual I-2
XhXh
Individual II-2
Xhy
Individual II-3
XHXh
***Use XH, Xh, and y for alleles***
What are the chances that Individual III-5 will have a son with the trait?
100%
Sex-Linked Recessive Disorder
Color-Blindness
Are you Red-Green Colorblind?
Pedigree Activity
(Left-Side of your IN)
Paste the pedigree above on the Left-Side of your IN and answer the following
questions in your IN.
Pedigree Activity
1. What type of pedigree is shown?
Autosomal Recessive
2. How many children of individuals II-2 and II-3 have attached
earlobes?
None
3. How many children of individuals III-3 and III-4 have
attached earlobes?
Three
4. Is individual I-2 homozygous or heterozygous for free
earlobes? Explain.
Heterozygous – because the trait was passed on, so the
recessive allele had to have been present
Pedigree Activity
5. Can you be certain of the genotype of individual
II-3? Explain.
No, the recessive allele could
be passed through individual II-2 or III-4
6. Predict the genotype and phenotype of individual
V-1.
genotype: homozygous recessive
phenotype: attached earlobes
7. Are any of the descendants of individuals I-1 and
I-2 homozygous for free earlobes (FF)?
No
Create a Pedigree
•
A man and woman marry. They have five children, 2 girls
and 3 boys. The mother is a carrier of hemophilia, an Xlinked recessive disorder. She passes the gene on to two
of the boys who died in childhood and one of the
daughters is also a carrier. Both daughters marry men
without hemophilia and have 3 children each (2 boys and
a girl). The carrier daughter has one son with hemophilia.
One of the non-carrier daughter’s sons marries a woman
who is a carrier and they have twin daughters.
•
Draw this pedigree. Label the genotypes of the
individuals above each circle or square. How many
people are carriers of hemophilia? How many actually
have the disease?