BIOB 375 1st Edition Lecture 19 Outline of Last Lecture II. Variations that arise from chromosome recombinationa. Cross-overb. Coupling vs. RepulsionOutline of Current Lecture III. Chromosome Rearrangementa. Duplicationb. Deletionc. Inversiond. TranslocationCurrent LectureVariation arise by chromosome rearrangementAll the tissues of an organism (except for gametes) have the same set of chromosomes and identical genetic materialKaryotype: the complete set of chromosomes possessed by an organism- Humans have two sets of chromosomes, one set from the male parent and the other from the female parent Most species have a characteristic number of chromosomes, each with a distinct size and structure Chromosome technologies make the detection of chromosome variation possible- Chromosome stain: to distinguish chromosomes by banding patterns- Feulgen’s reagent – a deep red color and uniform, hard to distinguish chromosome if they have similar length- Giemsa stainChromosome duplication- Gene dosage increase Phenotype changeHow can a chromosome duplicate in some regions?- Wild-type chromosomesChromosome deletion pseudodominance - Gene deleted phenotype change or even lethal - Deletion on chromosome 9 long arm – baby not developed fullyChromosome Inversion- Paracentric inversion – one arm is inverted- Pericentric inversion – centromere inverted If an individual possesses a normal chromosome and a chromosome with paracentric inversion –heterozygous for paracentric inversion, and a crossing-over occurs inside the inversion loop during meiosis, a chromosome bridge will form. - From chromosome bridge if crossing over occur inside the inversion loop, then duplication, deletion- No phenotype change if no position effectChromosome translocation- Balanced translocation- Unbalanced translocation- Robertsonian
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