Parental Dominance in Imprinted Genes

Research Paper Outline
Parental Dominance in Imprinted Genes

 

  • Survival of the fittest struggle begins inside a fertilized egg and throughout pregnancy
  • Parent’s DNA competes for gene control
  • Fetal genes are imprinted with either paternal or maternal molecules.
  • About 100 of the tens of thousands of genes are gender-specific but critical for survival
  • Imprinting mutations can lead to illness or death of a fetus or mother.

 

 

  • Azim Suranià biologist at University of Cambridge lab of Robert Edwards
  • In vitro fertilization
  • Parthenogenesisà healthy offspring created from an unfertilized egg
  • Can occur in fish and reptiles, but no known mammals
  • Studied parthenogenesis in mice.
  • Two sets of genes from males or two sets of genes from females = failed attempts
  • àmaternal and paternal genes each donate something crucial to offspring.

 

  • Offspring will each try to get more resources than available from parents
  • Example
  • Kinship Theoryà males & females want their offspring to survive, but their reproductive strategies are different, causing them to want different things for their offspring.
  • Female mammals almost always have multiple partners. Male partner will devote every possible resource to develop his offspring.
  • Females want to maximize amount of offspring – each could have a different father. Females give the embryo just what it needs to have enough for other offspring.
  • à

 

 

  • Imprints stamped on fetus’s genes can be turned on or off, and could change how the body reads genetic code.
  • Expressed genes are turned on only if inherited from a mother/father.
  • Fathers encourage growth
  • Mothers provide resources while in the womb. Inherited by mothers = slow the growth and allow her to conserve resources for embryo.

 

  • Lgf2 gene produces a protein key to growth.
  • Directs production of a receptor for the protein that keeps embryo growing
  • In mice, they are imprinted in mother and father
  • Mother = lgf2r on
  • Father = lgf2 on
  • The imprints cancel each other out. If one copy is taken out = effects on growth depending on which parent’s is taken out.
  • Turning off mom = large offspring
  • Turning off dad = dwarf offspring

 

  • Elizabeth Robertson – Columbia University – first to identify a printed gene.
  • Igf2 encouraging growth – demanding more from mom
  • Take out Igf2 with moms = normal
  • Take out Igf2 with dads = embryos only grew about 60% of normal size
  • à competition between mom and dad. When the gene is from a father, it is necessary for growth.

 

  • Imprinted genes can influence behavior via a number of mechanisms
  • Direct effects are illustrated by SNORD 115 and MAGEL2 = key genes underlying PWS
  • Imprinted genes regulate maternal supply and demand of nutrients
  • Imbalance in nutrient supply caused by lgf2 leads to abnormal offspring behavior
  • Imprinting genes may also be influenced by the environment; pre-natal and post-natal

Raeburn, Paul. “Genetic Battle of the Sexes”. Discovermagazine.com. 23 May 2014. Web. 29 Oct. 2014. <http://discovermagazine.com/2014/june/15-genetic-battle-of-the-sexes>

Davies, Jennifer. Dent, Claire. McNamara, Grainne. Isles, Anthony. “Behavioural Effects of Imprinted Genes”. Current Opinion in Behavioral Sciences Vol. 2. pp 28-33. Web. 4 Aug. 2014. 29 Oct. 2014. <http://www.sciencedirect.com/science/article/pii/S2352154614000102>

Dent, Claire. Isles, Anthony. “Brain-expressed imprinted genes and adult behavior: the example of Nesp and Grb10”. Mammalian Genome Vol. 25, Issue 1-2. pp 87-93. Web. 24 Aug. 2013. 29 Oct. 2014. <http://link.springer.com/article/10.1007/s00335-013-9472-0>

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