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Chapter 15 The Chromosomal Basis of Inheritance Chapter 15 The Chromosomal Basis of Inheritance Mendelian inheritance has its physical basis in the behavior of chromosomes during meiosis. Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan In the early 1900’s, he was the first scientist to want different varieties of fruit flies to study. Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan A white-eyed mutation showed up in his laboratory. Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan He bred his white-eyed fruit flies with “wild type” red-eyed fruit flies. Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan F1: all offspring had red eyes (therefore red is dominant) Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan F2: red:white = 3:1 (as expected) Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan F2: red:white = 3:1 But all the white-eyed flies were male. (very surprising) Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan F2 red:white = 3:1 But all the white-eyed flies were male. (very surprising) F2♀ red = 100% F2♂ red:white = 1:1 Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan Therefore the gene for white eyes is on the X chromosome. Chapter 15 The Chromosomal Basis of Inheritance Thomas Hunt Morgan XX = red-eyed female XX = red-eyed female XY = red-eyed male XY = white-eyed male Chapter 15 The Chromosomal Basis of Inheritance Recombination Chapter 15 The Chromosomal Basis of Inheritance Recombination Linked genes tend to be inherited together because they are on the same chromosome. Chapter 15 The Chromosomal Basis of Inheritance Recombination Independent assortment of chromosomes and crossing over produce genetic recombinations. Chapter 15 The Chromosomal Basis of Inheritance Recombination Recombination can be used to map genes on the chromosome. 1 centimorgan = 1% recombination Chapter 15 The Chromosomal Basis of Inheritance Sex Chromosomes Chapter 15 The Chromosomal Basis of Inheritance Sex Chromosomes Several patterns exist. XX vs. XY XX vs. X ZW vs. ZZ diploid vs. haploid Chapter 15 The Chromosomal Basis of Inheritance Sex Chromosomes Several patterns exist. XX vs. XY XX vs. X ZW vs. ZZ diploid vs. haploid Chapter 15 The Chromosomal Basis of Inheritance Barr Bodies Chapter 15 The Chromosomal Basis of Inheritance Barr Bodies A mammalian cell needs only one active X chromosome. In females, one of the two X’s is inactivated Chapter 15 The Chromosomal Basis of Inheritance Genomic Imprinting Chapter 15 The Chromosomal Basis of Inheritance Genomic Imprinting Individual genes may also be inactivated. Often this is done preferentially to the maternal or to the paternal copy of the gene. REPRODUCTIVE COMPETITION BETWEEN MALES AND FEMALES DAD DAD MOM MOM MOM KID KID KID KID KID KID Easygoing kids make mom’s job easier. Mom has more kids. DAD DAD MOM MOM MOM KID KID KID KID KID KID Difficult kids make mom’s job harder. Moms have fewer kids. Dad’s kids do better. DAD DAD MOM MOM MOM KID KID KID KID KID KID Genomic imprinting allows genes to have different effects based on whether they are passed through mom or through dad. DAD DAD MOM MOM MOM KID KID KID KID KID KID Chapter 15 The Chromosomal Basis of Inheritance Chromosomal Mutations Chapter 15 The Chromosomal Basis of Inheritance Chromosomal Mutations Alterations in chromosome number or structure cause some genetic disorders. Chapter 15 The Chromosomal Basis of Inheritance Chromosomal Mutations Aneuploidy Abnormal chromosome number Chapter 15 The Chromosomal Basis of Inheritance Chromosomal Mutations Polyploidy More than two complete sets of chromosomes Chapter 15 The Chromosomal Basis of Inheritance Chromosomal Mutations Deletion Duplication Inversion Translocation Chapter 15 The Chromosomal Basis of Inheritance Extranuclear Genes Chapter 15 The Chromosomal Basis of Inheritance Extranuclear Genes Mitochondria and chloroplasts contain some genes Chapter 15 The Chromosomal Basis of Inheritance Extranuclear Genes Mitochondria and chloroplasts contain some genes. These exhibit non-Mendelian inheritance (mother line only).
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