Polyploidy

Beschreibung

Year 1 BIO154 - Genetics I Karteikarten am Polyploidy, erstellt von Sophie Byrne am 18/04/2018.
Sophie Byrne
Karteikarten von Sophie Byrne, aktualisiert more than 1 year ago
Sophie Byrne
Erstellt von Sophie Byrne vor mehr als 6 Jahre
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Zusammenfassung der Ressource

Frage Antworten
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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