This presentation is about Genomic imprinting. Genomic imprinting is only found in eutherians. In next few slides we'll try to understand this phenomena.

1. Genomic Imprinting
Presented by:
Sanjay Kr. Vishwakarma

2. Genomic Imprinting
• Differential expression of a gene that depends on the sex of the
parent that transmitted the gene.
• Occurs in eutherians (placental, nonmarsupial) mammals.
• Males and females do not contribute the same genetic material to the
offspring.

3. • 260 imprinted genes in mice and 228 in humans (approx.)
• Involved in:
1. Fetal development
2. Brain development

4. Fetal Development
• Fetal growth genes:
Igf2
Igf2r
Grb10
H19
Gnas
Rasgrf
Mash2

5. Brain Development
• Prader Willi Syndrome- paternal chromosome deletion
• Angelman Syndrome- maternal chromosome deletion

6. Igf2

7. • Encodes a protein called insulin-like growth factor 2 (Igf2)
• Paternal copy of Igf2 is actively expressed in the fetus and placenta
• Maternal copy is completely silent
Igf2

8. • Paternal Igf2 allele (but not the maternal allele) promotes placental
and fetal growth.
• Without paternal copy of Igf2 a small placenta and low-birth-weight
offspring.
Igf2

9. Igf2

10. Prader Willi Syndrome
• Children with Prader–Willi syndrome have:
 Small hands and feet
 Short stature
 Poor sexual development
 Intellectual disability

11. • Children with Prader–Willi syndrome lack a paternal copy of genes
on the long arm of chromosome 15.
• The deletion of this region is always inherited from the father.
Prader Willi Syndrome

12. Angelman Syndrome
• Children with Angelman syndrome exhibit:
 Frequent laughter
 Uncontrolled muscle movement
 Large mouth
 Unusual seizures

13. • Children with Angelman syndrome lack a maternal copy of genes on
the long arm of chromosome 15.
• The deletion of this region is always inherited from the mother.
Angelman Syndrome

14. Multiple Choice Question

15. 1) Differential expression of the genetic material depending on its parentage of inheritance
gives
a) Penetrance
b) Expressivity
c) Imprinting
d) Non-penetrance
Answer: c

16. 2) How do Prader-Willi syndrome and Angelman syndrome differ?
a) Prader-Willi syndrome is associated with problems in the paternal chromosome, while
Angelman syndrome is associated with problems in the maternal chromosome.
b) Prader-Willi syndrome is associated with problems in the maternal chromosome, while
Angelman syndrome is associated with problems in the paternal chromosome.
c) Angelman syndrome is only caused by an error in imprinting.
d) Prader-Willi syndrome is only caused by an error in imprinting.
Answer: a

17. Thank You