Flashcards
Polyploidy
Cards in this deck (13)
- 1What are polyploids?Organisms with multiple (more than 2) complete sets of chromosomes.
i.e. 2n = diploid
3n = triploid
4n = tetraploid
5n = pentaploid
6n = hexaploid
--> 3n onwards = polyploids - 2What are the 3 broad "types" of polyploids?Autopolyploids
Allopolyploids
Palaeopolyploids - 3What are autopolyploids and how do they arise?Polyploids with multiple sets of chromosomes of the same type and origin.
Result from a mutation in chromosome number within a single species - 4What are allopolyploids and how do they arise?Polyploids with multiple sets of chromosomes of different type and origin.
Due to hybridisation b/w different but related species - 5What are the mechanics of polyploids (2 ways)?A: mutation in chromosome number within a single species
Diploid --> Autotetraploid (due to genome doubling)
B: formation of abnormal gametes with multiple sets of chromosomes
2 diploids INSERT DIAGRAM - 6What are palaeopolyploids?Organisms with polyploid ancestry that have reverted towards a diploid state in warious ways (e.g. deletion of duplicate gene copies)
- 7How is polyploidy tolerated in the animal kingdom? Which groups are stable polyploidy seen in?Not well tolerated.
10% of human spontaneous abortions are due to polyploidy.
Stable polyploidy only seen in some groups including fish and amphibians (often sterile and reproduce in special ways e.g. parthenogensis) - 8What is the frequency of polyploidy in flowering plants?High
1 in 100,000 offspring - 9What percentage of flowering plants have undergone polyploidisation during evolution?70%
Important in evolution of new plant species - 10What are 4 immediate effects of polyploidy?- Increased cell and organ size
- Greater vigor and biomass (usually)
- New phenotypes
- New patterns of gene expression - 11What are 2 advantages of polyploidy?- Gene redundancy:
e.g. masking recessive deleterious alleles by dominant wild type alleles in gametes and adult cells
e.g. diversification of gene function (redundant copies can evolve completely new functions - neofunctionalisation; or they can share diff aspects of the original funcntion - subfunctionalisation)
- Heterosis (hybrid vigor):
polyploids are more vigorous that their diploid progenitors e.g. fixed heterozygosity - 12What outcomes does meiosis in polyploids have?- Multiple ways of bivalents forming
- Quadrivalents can form
- Alleles on sister chromatids can end up in the same gamete (double reduction) - 13What is a challenge of polyploid meiosis?Instability caused by pairing difficulties in mitosis and meiosis
(produces aneuploid gametes containing missing or extra chromosomes)
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- Year 1 BIO154 - Genetics I Flashcards on Polyploidy, created by Sophie Byrne on 18/04/2018.
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- Sophie Byrne
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