Polyploidy

Question 1

polyploidy

Answer 1

genome doubling

- occurred in all major eukaryote groups

Question 2

autopolyploidy

Answer 2

doubling of all chromosomes

Question 3

allopolyploidy

Answer 3

hybridization event then chromosome doubling

Question 4

homeologs

Answer 4

pairs of genes duplicated by polyploidy

Question 5

significance of polyploidy

Answer 5

• novel phenotypes
• speciation- mechanism of instant speciation
• ecological diversification
• new alleles for gene evolution
• major effect on genome evolution

Question 6

polyploidy in plants

Answer 6

prominent and ongoing process

• many crop plants are polyploids
• tetraploids: canola, cotton, Durham wheat, peanut, coffee, tobaccos, potato
• hexaploidy: bread wheat, oat
• octoploid: strawberry

Question 7

polyploidy in animals

Answer 7

not as common due to sex determination and developmental defects

• some fish, insects, rare in mammals, NOT in birds
• ancient polyploidy during vertebrate evolution

Question 8

mechanisms of polyploidy formation

Answer 8

• union of unreduced gametes: produces tetraploid
• union of one reduced and one unreduced gamete: triploid
• • triploids are usually inviable
• – can be experimentally induced by colchicine treatment– microtubule inhibitor prevents cell division

Question 9

plant polyploids types that are studied

Answer 9

• formed 5000 - 2 million years ago
• • wheat, canola, cotton
• last 100 years
• • marsh grass
• • allows study in natural populations
• newly created
• • hybridization between two diploids then chromosome doubling by colchicine
• -frequently created by parents similar to natural polyploid species
• • study genomic and expression changes that occur upon polyploidy

Question 10

polyploidy and gene evolution

Answer 10

• gene loss immediately and over time
• chromosomal rearrangements
• changes in DNA methylation and histone modifications
• neo and sub functionalization

Question 11

gene expression changes in polyploidy

Answer 11

• up or down regulation of expression compared to parents
• silencing of one or both homeologs
• possible mechanisms include DNA methylation, histone modifications (methylation and deacetylation)
• can be organ specific or in response to stress conditions