Lecture 15 - Chromosomal Variations

Lecture 15 - Chromosomal Variations - Chromosomal...

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Unformatted text preview: Chromosomal Variations 1. Chromosome Number Variation 2. Chromosome Rearrangement Lecture 15 June 1 Chapter 9 http://www.youtube.com/watch?v=-_-P4t2jR1g Chromosome Mutation ¡ Refers to the variation in chromosome number and structure ¡ Includes: ± Changes in chromosome number or chromosome sets ¾ Aneuploidy (variation in number of individual chromosome) ¾ Polyploidy (variation in number of chromosome sets) ± Chromosome rearrangements ¾ Deletion or duplication of chromosomal segments ¾ Inversion ¾ Translocation ¾ other rearrangement either within or among chromosomes. ¡ Diploid species contain two sets of haploid chromosomes. Variations in Chromosome Number ¡ Aneuploidy ± Organisms that do not carry a correct set(s) of their basic chromosome number. ± Organism gains or loses one or more chromosomes, but not a complete set. ¡ Monosomy - The loss of a single chromosome. 2n-1 ¡ Nullisomy ± loss of both members of a homologous pair. 2n-2 ¡ Trisomy ± The gain of a single chromosome. 2n+1 ± 3 homologous copies ¡ Tetrasomy ± gain of two homologous chromosomes. 2n+2 ± 4 homologous copies ¡ Polysomy ± gaining more than one of a single chromosome. 2n+x ¡ Polyploidy ± More than two sets of the basic chromosome number are present. Origins of Aneuploidy ¡ Chromosome separate abnormally during mitosis or meiosis ± Disjunction: Separation of homologous chromosomes or sister chromatids. ± Non-disjunction: The failure of sister chromatids or homologous chromosomes to disjoin. Occurs in mitosis and meiosis. http://www.youtube.com/watch?v=r7LoczaDrVE&feature=related The Origin of Aneuploidy Æ nondisjunction Fig: 8 . 1 , K & C Aneuploidy Examples ± Human Turner Syndrome ¡ XO ± female that is missing a X chromosome with 45 chromosomes. ¾ Underdeveloped female with reduced intelligence ± Human Down Syndrome ¡ Polysomic individual (specifically trisomy 21)....
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This note was uploaded on 12/16/2011 for the course AGR 3303 taught by Professor Gallio during the Summer '08 term at University of Florida.

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Lecture 15 - Chromosomal Variations - Chromosomal...

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