polyploidy

Question 1

What are polyploids??

Answer 1

• Organisms with multiple (>2) complete sets of chromosomes.

Question 2

What are the types of polyploids? Describe each.

Answer 2

o Autopolyploids: multiple sets of chromosomes from the same time and origin – mutation in chromosome number within a single species.
o Allopolyploids: multiple sets of chromosomes of different type and origin – hybridisation between related but not the same species.
o Palaeopolyploids: organism with polyploidy ancestry but have reverted to a diploid state – deletion of duplicate gen copies etc.

Question 3

Describe Polyploidy in animals, give examples.

Answer 3

• Not well tolerated in animal kingdom – 10% of human spontaneous abortion is due to polyploidy.
• Stable polyploids only observed in certain groups, e.g. fish and amphibians.
• Often sterile & reproduce by specialised mechanisms e.g. parthenogenesis.
• E.g. salmon & trout – tetraploids & spotted salamander.

Question 4

Describe Polyploidy in plants:, give examples.

Answer 4

• Relatively high frequency – 1 in 100,000 offspring in plants.
• Est. over 70% flowering plants have undergone polyploidisation during evolutionary history.
• Important driving force in evolution of almost all flowering plants particularly in evolution of a new species.
• Commonly consumed: coffee, potato, kiwi, banana & peanuts.

Question 5

What are Immediate effects of polyploidy?

Answer 5

• Increased cell and organ size.
• Greater vigour and biomass (not always).
• New phenotypes.
• New gene expression patterns.

Question 6

What are the Advantages?

Answer 6

• gene redundancy:
  • Masking of recessive harmful alleles by dominant wild type alleles.
  • Diversification of gene function.
  • Redundant copies can share different aspects of the original function.

Question 7

What is polyploidy research used for?

Answer 7

• Food security – wheat = hexaploid.