13334641
Description
Flashcards by Sophie Byrne, updated more than 1 year ago
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Created by Sophie Byrne
over 6 years ago
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| Question | Answer |
| What 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 |
| What are the 3 broad "types" of polyploids? | Autopolyploids Allopolyploids Palaeopolyploids |
| What 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 |
| What 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 |
| What 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 |
| What are palaeopolyploids? | Organisms with polyploid ancestry that have reverted towards a diploid state in warious ways (e.g. deletion of duplicate gene copies) |
| How 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) |
| What is the frequency of polyploidy in flowering plants? | High 1 in 100,000 offspring |
| What percentage of flowering plants have undergone polyploidisation during evolution? | 70% Important in evolution of new plant species |
| What are 4 immediate effects of polyploidy? | - Increased cell and organ size - Greater vigor and biomass (usually) - New phenotypes - New patterns of gene expression |
| What 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 |
| What 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) |
| What 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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