BIO 370 Lecture Notes - Lecture 10: Salmonidae, Polyploid, Reproductive Isolation
• Variation is increased by rearrangement of chromosomes.
• Duplication
• Deletion
• Inversion
• Translocation
Polyploidy distribution across the diversity of life
• Angiosperms (flowering plants) – 30-80% of species
• Conifers (pines, firs, cypress and such) – 5% or fewer
• Tetrapods – rare, some amphibians.
• Fish – salmonids and carp.
• Non-vertebrates – not uncommon
• A very rough correlation with complexity of development.
Reproductive Isolation via Changes in Ploidy
Changes in chromosome number isolate populations genetically. Polyploidization can
produce instant reproductive isolation between parental and daughter populations due to
the formation of triploid hybrids: 4n X 2n → 3n
Any instance of polyploidization can create new sets of genees.
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Polyploidy
Advantages
• Provides duplicated genes which might fuel long-term diversification and evolutionary
success
• Gene redundancy masks lethal mutations
Disadvantages
• Intervening period of instability wherein polyploidy is disruptive of meiosis and
mitosis
• Change in cell size and structure affects stoichiometry of cell
• stoichiometry – literally easure of eleets – the study or measure of amounts of
substances in a reaction
A lot of plants are polyploids.
Dysploidy
• Change in chromosome number related to fission or fusion of entire chromosomes
• Does’t affet stoihioetry eause ???
• Would you guess it would be more or less stable than polyploidy?
• “tohioetry is’t affeted eause it’s just a ajor rearrageet. Eerythig is still
there but in different proportions.
• More stable than polyploidy, but still have problems of chromosomes lining up in the
zygote. **
Effects of Mutation on Fitness
Mutations are undirected; that is, they are generated at random.
If you demonstrated that mutations were directed and non-random you would corroborate
Laark’s hypothesis!
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