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Chapter 8: Human karyotypes and chromosome behavior The human karyotype y yp Metaphase spreads & karyotypes Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family The human karyotype y yp Banding & nomenclature The human karyotype y yp Banding & nomenclature The human karyotype y yp Size and gene density The human karyotype y yp Centromere position Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Animal karyotypes y yp Species-specific chromosome nr Animal karyotypes: y yp Related Animal karyotypes y yp Conservation of synteny The human karyotype y yp Centric (Robertsonian) fusions species with very different chr. nr The human karyotype y yp Centric (Robertsonian) fusions Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Sex chromosomes Dosage compensation Sex chromosomes Mammalian X inactivation D. melanogaster: doubled expression level from X in males C. elegans: halved expression level f om X in females from Mammals: Clonality & mosaïcism Doubled expression level from X in males and females + X inactivation in females = “lyonisation” y Calicot cat Role of XIST Random versus imprinted Xinactivation Sex chromosomes Mammalian X inactivation Sex chromosomes Mammalian X inactivation Clonality & mosaïcism Role of XIST Random versus imprinted Xinactivation Sex chromosomes Evolution Sex chromosomes originated from regular autosome by acquisition of sex determining gene (SRY) Chromosomal inversions “isolate” male-beneficial, f female-deleterious l d l t i haplotypes h l t iincluding l di SRY Absence of recombination causes progressive degradation of the Y chromosome Loss of genes on the Y drives progression of X inactivation Sex chromosomes maintain meiotic pairing in pseudoautosomal region. region Divergence g of X and Y by y successive inversions Divergence g of X and Y by y successive inversions Sex chromosome: Tracing human history through the Y chromosome Progression g of X inactivation from old to young strata Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Spontaneous p abortions & chromosmal abnormalities Spontaneous p abortions & chromosomal abnormalities Aberrant euploidies: Triploids Tetraploids Aneuploidies: A l idi Trisomies Monosomies (early lethality) Structural anomalies Translocations (Balanced or unbalanced) … Down syndrome y Symptoms Down syndrome y Chromosomal non-disjunction Non crossover bivalents Down syndrome y Effect of mother’s age Down syndrome y Prenatal diagnosis Down syndrome y Trisomic segregation Sex chromosome abnormalities Frequency Trisomy X Dounble Y Klinefelter syndrome Turner syndrome Environmental effects on non disjunction Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Deletions Phenotypic consequences Deletions Causes Large: dominant Small: recessive Autism Spectrum Disorders (ASD) Chromosomal breakage and reunion Ectopic recombination between direct repeats Ectopic p recombination between direct repeats Deletions Deletion mapping Deletions Deletion mapping Duplications p Phenotypic effects Milder than deletions Example: Bar Tandem Duplications p Unequal crossing over Tandem duplications p Red-green color blindness Overview Inversions Causes The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Chromosome breakage and inversion Ectopic recombination between inverted repeats Ectopic p recombination between inverted repeats Inversion heterozygotes yg Inversion loops Inversion heterozygotes yg No recombination Paracentric inversion heterozygotes: recombination Cross-over suppressors Pericentric inversion heterozygotes: recombination Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Cross-over suppressors Reciprocal p translocations Definition Reciprocal p translocations Causes Chromosome breakage and translocation Ectopic recombination Reciprocal p translocations Semisterility Reciprocal p translocations Robertsonian translocations Reciprocal p translocations and trisomy 21 ( (Translocation complexes p in Oenothera) Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Overview Position effect variegation The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Polyploidy yp y in plant evolution Monoploid versus haploid number Common in plants, including domestic species (Ù increased yield) Rare in animals Triploids Sexual versus asexual polyploidization Autopolyploids p yp and allopolyploids Autopolyploids p yp and allopolyploids Autopolyploids p yp and allopolyploids Monoploid organisms Use of monoploidy p y in p plant breeding Occur naturally in some insects (males) Allows selection of recessive m tations in plants mutations Is revertible with colchicine Overview The human karyotype Animal karyotypes Sex chromosomes Chromosome abnormalities in human pregnancies Chromosomal deletions and duplications Genetics of chromosomal inversions Ch Chromosomal l translocations l i Position effect variegation Polyploidy in plant evolution Genome evolution in the grass family Conserved synteny in Graminae
