It is ppt based on pedigree analysis for class 12 investigatory project

1. Pedigree Analysis
Dr. Monisha Banerjee
Professor
Molecular & Human Genetics Lab
Department of Zoology
University of Lucknow
Lucknow

2.  A pedigree is a
pictorial representation
of a family history.
 It is an important tool
for studying inherited
diseases and other
traits.
 Pedigree analysis uses
family trees and
information about
affected individuals .
What is a Pedigree?
1 2 3 4 5 6
1 2 3 4 5 6 7 8 9
1 2 3 4 5
1 2
I
II
III
IV

3. Most common signs and symbols
used in pedigree analysis

4. A Typical Pedigree
Normal
Female
Normal
Male
Mating
1st born
Siblings
Affected
I
II

5. Basic patterns of inheritance
•Autosomal, recessive
•Autosomal, dominant
•X-linked, recessive
•X-linked, dominant (very rare)
•Y-linked

6. Autosomal vs. sex-linked traits
Autosomal traits are caused by genes on
autosomes (chromosome #1- #22)
e.g., we speak of autosomal recessive or
autosomal dominant traits or diseases.
Sex-linked traits are caused by genes on
the sex chromosome (X or Y)
e.g., we speak of X-linked recessive or X-
linked dominant traits or diseases.

7. Recessive inheritance
If d is the disease allele and D is
normal, then only dd genotypes
are affected
Typically not seen in every
generation
Affected offspring can be born to
unaffected parents

8. Dominant inheritance
If D is the disease allele and d is
normal, then only dd genotypes are
disease free*
Dominant trait/disease found in every
generation*
Affected offspring never** born to
unaffected parents
*Assuming 100% penetrance
**Assuming no new mutation

9. Autosomal recessive
Trait is rare in
pedigree
Trait often skips
generations (hidden
in heterozygous
carriers)
Trait affects males
and females equally

10. Autosomal recessive diseases in humans
Most common ones
• Cystic fibrosis
• Sickle cell anemia
• Phenylketonuria (PKU)
• Tay-Sachs disease

11. Trait is common in the pedigree.
Trait is found in every generation.
 Appears in both sexes in equal frequency.
Affected individuals transmit the trait to ~1/2 of their
children (regardless of sex).
Autosomal dominant

12. ACHONDROPLASIA
(a sketelal disorder causing dwarfism)
Autosomal Dominant disease in humans
Huntington’s disease

13. X-linked recessive
Trait is rare in pedigree.
Trait skips generations.
Affected sons are usually born
to unaffected but carrier
mothers.
Affected fathers DO NOT pass
trait to their sons.
Males are more often affected
than females.

14. Female carrier mates with normal male
F
XNXN
Y
XN
Half* her daughters will be carriers
Half* her sons will be affected
x M
XNY
Eggs
Sperm
XN
M
XNY
normal normal
M
XAY
affected
F
XAXN
carrier
X-linked
recessive
disease
XA
F
XNXA

15. X-linked recessive diseases
Glucose-6-Phosphate Dehydrogenase deficiency
 Hemophilia in European royalty
Duchenne Muscular Dystrophy

16. Partial pedigree analysis of haemophilia in royal
families of Europe
Only males develop the disease!

17. X-linked dominant
Trait is found in every
generation
 Affected sons must have an
affected mother
Affected mother if
heterogygous will pass the
trait to ½ of the sons and ½
of their daughters
Affected fathers pass trait to
ALL of their daughters
Males and females are
equally likely to be affected

18. Affected males mates with normal females
Y
XN
• All his daughters will be affected
• None of his sons will be affected
F x M
XNXN XAY
Eggs
Sperm
XA
M
XNY
normal
M
XNY
normal
F
XNXA
affected
F
XNXA
affected
X-linked dominant disease
XN

19. X-linked dominant diseases
X-linked dominant diseases are extremely
unusual
Often, they are lethal (before birth) in males
and only seen in females
eg. Incontinentia pigmenti (skin lesions)
eg. X-linked rickets (bone lesions)
eg. Hypophosphatemia

20. Y-Linked Inheritance
 Traits are found in every
generation
 Traits on the Y chromosome
are only found in males,
never in females.
 The father’s traits are passed
to all sons.
 Dominance is irrelevant:
there is only 1 copy of each
Y-linked gene
(hemizygous).

21. Goals of Pedigree Analysis
 Determine the mode of inheritance:
dominant, recessive, partial dominance,
sex-linked, autosomal, mitochondrial,
maternal effect.
 Predict the risk of disease in future
offspring in a family (genetic counseling).

22. Thank you