04BIS10110152013RecombinLect4

Lrodriguez 6 human x chromosome illustrates gene

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Unformatted text preview: ssortment). How can linkage be used to understand gene How and chromosome structure? and BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 6 Human X Chromosome Illustrates Gene Linkage ­ Some of the X-linked Some p genes discussed previously have been mapped on the human X chromosome. Note that the Hemophilia A gene is linked to linked colorblindness on the long (q) arm of the X. long Ocular albinism q BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 7 Gene/Mutant Nomenclature ­ To simplify the description of genetic crosses involving multiple loci, To geneticists have developed the shorthand nomenclature shown below. With this nomenclature, the locus is given a one- or two-letter italic designation based on the mutant or alternate allele. The recessive mutant allele is indicated with lower case letters while the normal (wild type) allele is indicated with capital letters or simply with a "+" sign. For type) example, the fruit fly typically has red eyes (+). An alternate form of the red eye allele is the purple eyed (pr) phenotype: red ALLELIC FORMS FOR EYE COLOR AND WING SHAPE Wild type (normal) red eyes = Pr, pr+ or + red Pr, normal wing shape = Vg, vg+ or + normal Vg, Mutant (defective) purple eyes = pr purple pr vestigial (stubby) wing shape = vg vestigial vg BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 8 Morgan’s analysis eye color and wing shape ­ Two genes close together on the same chromosome behave Two as one gene (i.e., they do not assort independently). as BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 9 Linkage or eye color and wing shape alleles ­ As shown previously, Mendel...
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