Biology Chapter 12 Powerpoint

Factor viii now available via biotechnology

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Unformatted text preview: gy Hemophilia Pedigree 14 Human X-Linked Disorders: Fragile X Syndrome 15 Chromosomal Inherit Due to base-triplet repeats in a gene on the X Due chromosome chromosome CGG repeated many times 6-50 repeats – asymptomatic 230-2,000 repeats – growth distortions and 230-2,000 mental retardation mental Inheritance pattern is complex and Inheritance unpredictable unpredictable Gene Linkage 16 17 Chromosomal Inherit Gene Linkage When several genes of interest exist on the When same chromosome same Such genes form a linkage group Tend to be inherited as a block If all genes on same chromosome: ­ Gametes of parent likely to have exact allele Gametes combination as gamete of either grandparent combination ­ Independent assortment does not apply If all genes on separate chromosomes: ­ Allele combinations of grandparent gametes Allele will be shuffled in parental gametes will ­ Independent assortment working Linkage Groups 18 19 Chromosomal Inherit Constructing a Chromosome Map Crossing-over can disrupt a blocked allele pattern on a Crossing-over chromosome chromosome Affected by distance between genetic loci Consider three genes on one chromosome: If one at one end, a second at the other and the third in the middle ­ Crossing over very likely to occur between loci ­ Allelic patterns of grandparents will likely to be disrupted in Allelic parental gametes with all allelic combinations possible parental If the three genetic loci occur in close sequence on the If chromosome chromosome ­ Crossing over very UNlikely to occur between loci ­ Allelic patterns of grandparents will likely to be preserved in Allelic parental gametes parental Rate at which allelic patterns are disrupted by crossing over: Indicates distance between loci Can be used to develop linkage map or genetic map of Can chromosome chromosome Crossing Over 20 Complete vs. Incomplete Linkage 21 Chromosome Number: Polyploid...
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