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Chapter 8 - 204-325 1 Summary of the Last Lecture Ordered...

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Unformatted text preview: 204-325 1 Summary of the Last Lecture Ordered Tetrads in haploid eukaryotes can be used to map the distance between a gene and its centromere. Ordered and unordered Tetrads in haploid eukaryotes can be used to map the distance between two genes. Rare mitotic recombination can result in mutant patches of somatic cells. Mitotic recombination can be used to map genes. Pedigree analysis, molecular markers, fluorescent in situ hybridization, and radiation hybrid are used to map human genes. 2 Today's Topics 1. Variations in Chromosome Structure: deletion, duplication, inversion and translocation 2. Variations in Chromosome Number: aneuploidy, monoploidy, and polyploidy 3 Topic 1 Variations in Chromosome Structure: deletion, duplication, inversion and translocation 4 Deletion of a Chromosome Segment 5 Cytological Effects of Heterozygosity for Deletion 6 Cri-du-chat Syndrome: Chromosome 5 has a deletion Mental Retardation 7 Duplication: a Chromosome Segment is Repeated 8 Several Forms of Chromosome Duplications 9 Duplications Responsible for Bar Phenotypes 10 Unequal Crossing-over Gives Rise to Duplication and Deletion 11 Inversions 12 Crossing-over in Heterozygous Paracentric Inversion 4 3 X Semi Sterile X 13 Crossing-over in Heterozygous Pericentric Inversion X Semi Sterile X 14 Animation 1: Meiosis of Pericentric Inversion 15 Translocations 16 Meiosis of Reciprocal Translocation Heterozygote -JKL -DEF X X -IHG -ABC X X Semi Sterile 17 Animation 2: Meiosis of Translocation 18 Structure Variation Produced by Breakages 19 Structure Variation Produced by Unequal Crossover 20 Topic 2 Variations in Chromosome Number: Aneuploidy, monoploidy and polyploidy 21 A Diploid (2N) and Examples of Aneuploidy Aneuploid 22 Non-disjunction Gives Rise to Aneuploidy 23 Meiotic Segregation of a Trisomic Individual 24 Aneuploidy in Human 25 Down Syndrome: Trisomy-21 1: 700 26 Down Syndrome 27 Increased Risk of Down Syndrome with more Mature Mother 28 Robertsonian Translocation 14 21 29 Segregation of Heterozygous Robertsonian Translocation X X X 30 Animation 3: Down Syndrome 31 Turner Syndrome (XO): Monosomy for X 32 Klinefelter Syndrome (XXY): Trisomy 33 Patau Syndrome is due to Trisomy-13 1:5000 Cleft lip, polydactyly, developmental retardation, lethal before 3 month 34 Edwards Syndrome is due to Trisomy-18 1:4000 Clenched fists, elongated skull, malformed ear, developmental retardation 90% lethal by 6 months 35 Monoploids, Diploids and Polyploids are Euploids Euploid 36 Hexaploidy in Wheat: an Example of Allopolyploidy 37 Diploid (2N, left) and Tetrapolid (4N, right) Grapes 3N, 5N, 7N etc plants are almost sterile Seedless fruits 38 Fate of One Million Implanted Human Zygotes 50% 0.6% 39 Euploidity and Aueupolidity Euploid Aneuploid 40 Summary Chromosomal mutations are variations from wild-type condition in numbers or structures. Four major chromosomal structure alternations are deletions, duplications, inversions and translocations. Aneuploid has chromosome number that is not the exact multiple of wild-type chromosome set, such as in nullisomy, monosomy, trisomy and tetrasomy. Monoploid, diploid and polyploid are considered euploid (multiples of complete sets of chromosomes). 41 ...
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