Polyploid

Plants

1. History
   1. Oenothera
   2. Major Crops: coffee, wheat, oat, cotton, tobacco, potato..
2. Types
   1. auto, allo. Amphidiploid is true auto tetraploid
3. Pattern of inheritance
   1. Disomic - 1:2:1 - forms bivalents
   2. Tetrasomic - 1:8:18:8:1 - forms multivalent
   3. allo is less stable, why?
4. Frequency of Polyploid in plants
   1. Most genomes (>70%) have undergone one or more rounds of polyploidisation in the history
   2. detection using guard cell size in stomata; based on haploid crm number
   3. Auto polyploid is more common than allo. why? detected using co dominant marker (isozyme?!)
5. Formation of polyploid
   1. Crm doubling in somatic cell
   2. Triploid Bridge: Failure of crm reduction in egg cell formation during meiosis (unreduced gamete): yields triploid > if viable > produce triploid egg at particular proportion > cross with diploid > produce tetraploid
   3. Endosperm Balance Hypothesis (EBN): Should be 2(maternal):1(paternal) for the normal function of endosperm. EBN is useful in predicting the ploidy of unknown species(!)
6. Multiple origin of polyploidy
   1. direct doubling
   2. intermittent crossing with polyploids
   3. In general, polyploidy maintains high levels of genetic variation
7. Impact at cellular and organismal level
   1. Increased cell (guard, pollen) size than the diploid
   2. Why Apomixis is common in polyploids??
   3. Polyploidy is a trigger of gender dimorphism in plans (monoeceous, dioeceous)
   4. In general the physiological activity is raised
   5. And there is no altitude/latitude relation with ploidy level but if the polyploidy is heterozygous, it might be more tolerable to extreme conditions
   6. Deepening on the type of interaction, polyploidy response better than a diploid with animal (kind of defense)
8. Impact at genome level
   1. Translocations occur because of polyploidization: Nicotiana
   2. Higher C value (but same genome size)
   3. The duplicated genes
      1. Both remain functional
      2. One copy degenerates
      3. one of the copies get diverged to function differently (neo-functionalisation and sun-functionalisation)
   4. Rate of sequence diversity in relation with diploid is dynamic with genes and species
   5. Gene loss can occur rapidly in polyploids
   6. TEs and nuclear cytoplasmic interactions tend to have more effcts in polyploidy.

Animals

In general less occurrence

1. Detection
   1. Cell and nucleus size
   2. Meiotic crm behavior
   3. Protein electrophoresis
2. Why animal has less distribution if polyploidy?
   1. Disruption of sex determination
   2. Meiotic disjunction leads to unbalanced games > tripoid bridge is stopped > sterile. so no way of formation of tetraploid
   3. Impossible interploidy crosses
   4. disruption of development

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