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2016-06-23T08:42:09Z

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Raj at 19:20, 3 January 2010

2010-01-03T19:20:42Z

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==Plants==
# History
## Oenothera
## Major Crops: coffee, wheat, oat, cotton, tobacco, potato..
# Types
## auto, allo. Amphidiploid is true auto tetraploid
# Pattern of inheritance
## Disomic - 1:2:1 - forms bivalents
## Tetrasomic - 1:8:18:8:1 - forms multivalent
## allo is less stable, why?
# Frequency of Polyploid in plants
## Most genomes (>70%) have undergone one or more rounds of polyploidisation in the history
## detection using guard cell size in stomata; based on haploid crm number
## Auto polyploid is more common than allo. why? detected using co dominant marker (isozyme?!)
# Formation of polyploid
## Crm doubling in somatic cell
## '''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
## 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(!)
# Multiple origin of polyploidy
## direct doubling
## intermittent crossing with polyploids
## In general, polyploidy maintains high levels of genetic variation
# Impact at cellular and organismal level
## Increased cell (guard, pollen) size than the diploid
## Why Apomixis is common in polyploids??
## Polyploidy is a trigger of '''gender dimorphism''' in plans (monoeceous, dioeceous)
## In general the physiological activity is raised
## And there is no altitude/latitude relation with ploidy level but if the polyploidy is heterozygous, it might be more tolerable to extreme conditions
## Deepening on the type of interaction, polyploidy response better than a diploid with animal (kind of defense)
# Impact at genome level
## Translocations occur because of polyploidization: Nicotiana
## Higher C value (but same genome size)
## The duplicated genes
### Both remain functional
### One copy degenerates
### one of the copies get diverged to function differently (neo-functionalisation and sun-functionalisation)
## Rate of sequence diversity in relation with diploid is dynamic with genes and species
## Gene loss can occur rapidly in polyploids
## TEs and nuclear cytoplasmic interactions tend to have more effcts in polyploidy.
==Animals==
In general less occurrence
# Detection
## Cell and nucleus size
## Meiotic crm behavior
## Protein electrophoresis
# Why animal has less distribution if polyploidy?
## Disruption of sex determination
## Meiotic disjunction leads to unbalanced games > tripoid bridge is stopped > sterile. so no way of formation of tetraploid
## Impossible interploidy crosses
## disruption of development

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[[Category:Readings]]

Polyploid - Revision history

Raj at 08:42, 23 June 2016

Raj: 1 revision imported

Raj at 19:20, 3 January 2010