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The importance of genomic imprinting


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The importance of genomic imprinting

  2. 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. 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. 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. 5.  Clip going into short detail of each syndrome.
  7. 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. 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. 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. 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.