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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parental generation male Parental generation female F 2 female progeny had red eyes, only males had white eyes F 1 generation male F 1 generation female F 1 progeny all had red eyes Parental generation male Testcross F 1 generation female The testcross revealed that white-eyed females are viable. Therefore eye color is linked to the X chromosome and absent from the Y chromosome 2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. X chromosome Y chromosome 2.8 µm © BioPhoto Associates/Photo Researchers, Inc. 3

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Kenneth Mason Nucleus Allele for orange fur is inactivated Allele for black fur is inactivated X chromosome allele for orange fur Inactivated X chromosome becomes Barr body Second gene causes patchy distribution of pigment: white fur = no pigment, orange or black fur = pigment X chromosome allele for black fur Inactivated X chromosome becomes Barr body 5

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parental All parentalRecombinant Meiosis II No recombinant Meiosis II Parent generation F 1 generation Meiosis with Crossing over Meiosis without Crossing over Crossing over during prophase I No crossing over during prophase I 6

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 18% recombinant frequency Cross-fertilization recessive allele (black body) dominant allele (gray body) recessive allele (vestigial wings) dominant allele (normal wings) Parental generation F 1 generation Testcross Testcross male gamete 415 parental wild type (gray body, long wing) 92 recombinant (gray body, vestigial wing) F 1 generation female possible gametes 88 recombinant (black body, long wing) 405 parental mutant type (black body, vestigial wing) = 0.18 total recombinant offspring 18 cM between the two loci 7

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Recombination Frequency Physical Distance on a Chromosome 8

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parental Recombinant A a B b C c ac bA B C 9

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Colorado Genetics Laboratory, University of Colorado Denver XY 10

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Normal male X XXX Y O Nonviable XO Female gametes undergo nondisjunction Triple X syndrome XX XXY Klinefelter syndrome OY Turner syndrome 11

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amniotic fluid Hypodermic syringe Uterus 12

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cells from the chorion Suction tube Uterus Ultrasound device Chorionic villi 13