Extranuclear Inheritance

• extranuclear inheritance


  genetic information is transmitted through the cytoplasm rather than genes
• maternal effect


  the maternal genotype determines the phenotype of the progeny
• the majority of the cytoplasm in zygotes comes from the ovum
• maternal to zygotic transition


  stage where development comes under the control of the zygote rather than the maternal genes
• stages of embryonic development in Drosophila


  1. diploid zygote
  2. syncytial blastoderm
  3. migration of nuclei to outer cortex
  4. nuclei enclosed by cell membrane
• maternal effect genes determine zygote polarity in Drosophila
• bicoid gene


  maternal effect gene that controls anterior development in Drosophila, mutations produce nonviable embryos
• nanos gene


  maternal effect gene that controls posterior development
• organelle heredity


  passing of DNA-containing organelles to offspring through cytoplasm
• Carl Correns


  studied leaves of the Mirabilis jalapa to determine the inheritance of leaf color is determined by the plant that contributed the ovule
• Mary B. and Hershel K. Mitchell


  discovered fungal strain called poky and found the phenotype of the parent contributing cytoplasm dictated the phenotype of the offspring
• endosymbiotic theory


  proposed by Lynn Margulis; theory that states mitochondria and chloroplasts were once free-living protobacteria that were engulfed by eukaryotic cells and coevolved
• cpDNA


  chloroplast DNA
• mtDNA


  mitochondrial DNA
• heteroplasmy


  describes a mixture of normal and mutant organelles in cytoplasm
• mitochondrial genetic disorders are often hard to identify because there are many variables
• for an issue to be attributed to a mitochondrial mutation, it must

  1. exhibit a maternal inheritance pattern
  2. show a specific change in a mitochondrial gene
  3. reflect a deficiency in bioenergy
• Leber's Hereditary Optic Neuropathy


  mitochondrial disorder resulting in sudden bilateral blindness
• Kearns Sayre Syndrome


  mitochondrial disorder causing a loss of vision and hearing as well as heart problems as a result of large deletions, cannot survive if homoplasmic
• Leigh syndrome


  mitochondrial disorder that causes the progressive loss of movement and mental function, can be treated with mitochondrial replacement therapy
• mitochondrial disorders can skip generations or have variable expressivity due to random distribution of organelles