1. Ryan Yerger
BIOL-101
THE IMPORTANCE OF GENOMIC IMPRINTING

2. IMPRINTING
 Most genes.
 Inherit working copies.
 One from mom, other
from dad.
 Imprinting.
 Inherit one working
copy.
 Depending on gene,
copy from mom or dad is
epigenetically silenced.
 Silencing occuring
through addition of
methyl groups during
egg/sperm formation

3. IMPROPER IMPRINTING
 Individual typically has one active
copy.
 Improper imprinting can lead to two
active copies or two inactive copies.
 Developmental abnormalities, cancer, etc.
 Prader-Willi and Angelman
Syndrome.
 Very different, but linked to chromosome
15.

4. PRADER-WILLI AND ANGELMAN
 Prader-Willi Syndrome  Angelman Syndrome
 Symptoms  Symptoms
 Learning difficulties,  learning difficulties,
short stature, compulsive speech problems,
eating. seizures, jerky
 Missing gene activity movements, unusually
happy disposition.
that comes from Father.
 Missing gene activity that
 Father’s copy missing,
comes from Mother.
or two maternal copies.
 Mom’s copy is missing,
two paternal copies.

5.  http://www.youtube.com/watch?v=0ff4o6ttkmU
 Clip going into short detail of each syndrome.

6. BECKWITH-WIEDEMANN SYNDROME

7. GENETIC CONFLICT HYPOTHESIS
 supposes that imprinting grew out of a
competition between males for maternal
resources.
 Is in the interest of the Father’s genes to
produce larger offspring.
 Best for the Mother’s genes if all of offspring
survive to adulthood and reproduce.

8. GENETIC CONFLICT HYPOTHESIS CONT’D
 Many imprinted genes deal with growth and
metabolism.
 Paternalimprinting favors larger offspring.
 Maternal imprinting favors smaller offspring.
 Maternal and Paternal work in same growth
pathways.
 Sets up epigenetic battle between parents.
 Parental tug-of-war.

9. BECKWITH-WIEDEMANN SYNDROME
 Igf2 gene codes for a hormone that
stimulates growth during embryonic and fetal
development.
 Methyl tags usually silence maternal Igf2 gene.
 DNA mutation (epimutation) can activate it.
 Causes BWS.
 Most common feature is over-growth.
 Babies born larger than 95% of peers.
 Increased risk of cancer.

10. BECKWITH-WIEDEMANN SYNDROME CONT’D
 Occurs 1 in 15,000 births.
 Babies conceived in laboratories with help of
artificial reproductive technology (ART), rate
of BWS goes up to 1 in 4,000.
 Safety of ART laboratory procedures into
further investigation.