rav65819_ch13_237-254

rav65819_ch13_237-254 - ; 13 4 mm chapter Chromosomes,...

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;;;;;;;; 13 4 mm chapter Chromosomes, Mapping, and the Meiosis–Inheritance Connection introduction MENDEL’S EXPERIMENTS OPENED the door to understanding inheritance, but many questions remained. In the early part of the 20th century, we did not know the nature of the factors whose behavior Mendel had described. The next step, which involved many researchers in the early part of the century, was uniting information about the behavior of chromosomes, seen in the picture, and the inheritance of traits. The basis for Mendel’s
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principles of segregation and independent assortment lie in events that occur during meiosis. The behavior of chromosomes during meiosis not only explains Mendel’s principles, but leads to new and different approaches to the study of heredity. The ability to construct genetic maps is one of the most powerful tools of classical genetic analysis. The tools of genetic mapping developed in flies and other organisms in combination with information from the human genome project now allow us to determine the location and isolate genes that are involved in genetic diseases. concept outline 13.1 Sex Linkage and the Chromosomal Theory of Inheritance Morgan correlated the inheritance of a trait with sex chromosomes The gene for eye color lies on the X chromosome 13.2 Sex Chromosomes and Sex Determination In humans, the Y chromosome generally determines maleness Some human genetic disorders display sex linkage Dosage compensation prevents doubling of sex-linked gene products X chromosome inactivation can lead to genetic mosaics 13.3 Exceptions to the Chromosomal Theory of Inheritance Mitochondrial genes are inherited from the female parent Chloroplast genes may also be passed on uniparentally 13.4 Genetic Mapping Genetic recombination exchanges alleles on homologues Recombination is the basis for genetic maps Multiple crossovers can yield independent assortment results Three-point crosses can be used to put genes in order Genetic maps can be constructed for the human genome 13.5 Selected Human Genetic Disorders Genetic disorders can be due to altered proteins Nondisjunction of chromosomes changes chromosome number Genomic imprinting depends on the parental origin of alleles
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Some genetic defects can be detected early in pregnancy 237 rav65819_ch13_237-254.indd 237 rav65819_ch13_237-254.indd 237 11/16/06 3:25:44 PM 11/16/06 3:25:44 PM 13.1 Sex Linkage and the Chromosomal Theory of Inheritance A central role for chromosomes in heredity was first suggested in 1900 by the German geneticist Carl Correns, in one of the papers announcing the rediscovery of Mendel’s work. Soon after, observations that similar chromosomes paired with one another during meiosis led directly to the chromosomal theory of inheritance, first formulated by the American Walter Sutton in 1902. Parental generation female
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch13_237-254 - ; 13 4 mm chapter Chromosomes,...

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