chromosome-number - Anueploidy vs. polyploidy Chromosomal...

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Chromosomal Variation Changes in chromosome number Anueploidy vs. polyploidy • Changes in the number of entire chromosome sets – polyploidy • Changes in copy number for single chromosomes – anueploidy Ploidy Levels • Let x = number of chromosomes in basic set – x = monoploid (haploid) – 2x = diploid – 3x = triploid – 4x = tetraploid – 6x = hexaploid Polyploidy • Polyploids are common in plants – Many important crop plants are polyploids • Genomics has shown evidence for ancient polyploid events in many species currently regarded as diploids – Vertebrates are likely an ancient tetraploid lineage
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• Not uncommon for polyploids to be viable, but sterile – If chromosomes do not occur in pairs, problems at meiosis – Such individuals are usually sterile • If double basic chromosome set, normal meiosis occurs Hybrid formed from two different species, resulting chromosomes do not pair and hence segregate randomly at meiosis Gamete Required Matching gamete By simply doubling the chromosome sets, we now have a pair for each homologue and hence proper segregation Allo- vs. Autopolyploids
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chromosome-number - Anueploidy vs. polyploidy Chromosomal...

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