Chapter 15 Pgs 286 194 and 297 302 Pages 303 304 1 3 5 7 1 22 chromosomes are autosomes 23 is the sex chromosomes Sex linked genes examples in mammals o SRY Gene Sex determining Region of Y chromosome o DAX gene DosAge sensitive gene on X chromosome Sex linked traits disorders due to gene on a sex chromosome X or Y Often Recessive o Female XX carrier if heterozygous or affected if homozygous o Male XY Hemizygous affected if have gene Ex color blindness hemophilia Fig 15 7 Discovery Timeline 1860 s Mendel s law of inheritance 1870 1890s Physical process of mitosis meiosis discovered 1902 Sutto and Boveri propose o Chromosomal theory of inheritance o Mendelian genes have specific loci positions on chromosomes 1928 Griffith recognized a principle Process Proposes Heritable substance transforms cells Transformation change the genotype and phenotype due to assimiliation of external DNA Pathogenic strain o Living S smooth Strain o Kills the mouse Non Pathogenic Strain o Living R rough cells o Mouse healthy Heat killed S cells control o Mouse healthy Mixture of heat killed S cells and living R cells o Mouse dies o Living S cells are in the mouse 1944 Avery McCarty MacLeod experiments o Only DNA transforms cells o Living R S cell protein Mouse healthy o Living R S cell RNA Mouse Healthy o Living R S cell DNA Mouse DIES Only DNA transforms bacteria 1950 Erwin Chargraff o adenines thymines o guanines cytosines 1952 Hershey and Chase Figure 16 4 1 o Bacteria and Bacteria Phages o Soaked in Radioactive Sulfur Proteins have sulfur No radioactivity was found o Soaked in Radioactive Phosphorus DNA has Phosphorus Pellet ends up having radioactivity Rosaline Franklin X ray crystallography o X ray diffraction pass X rays through aligned DNA fibers produces shadows of structure Watson and Crick 1953 o Radically different structure o Novel features Tomas Hunt Morgan early 1900 s Provided Physical evidence for genes associating with chromosome Used Drosophila melanogaster Fruit Fly Studied Sex linked traits Genetic Variation Recombination of Genes 1 Independent assortment are combines unlinked genes Test Cross Heterozygous and a homozygous Recessive If Testcross results in Parental Type Greater than 50 offspring phenotypes Recombinant Type much less than 50 offspring phenotypes new combos Then Linked genes genes located on the same chromosome tend to be inherited together but not always due to crossing over Abnoraml Chromosome Number Nondisjuction When homologous chromosomes or sister chromatids do NOT separate 1 Aneuploidy offspring w abnormal of a particular chromosome monosomy trisomy a Down Syndrome Tisomy 21 b Klinefelter Syndrom XXY c Turner Syndrome XO 2 Polyploidy offspring w more than 2 complete chromosome sets a Triploidy 3N Tetraploid 4N etc Testing for Genetic Disorders 1 Identify Carriers a Use in vitro fertilization and screen embryos 2 Fetal Testing Fig 14 18 a Amniocentesis b Chlorionic Villus Sampling c Ultrasound 3 Newborn Screening a PKU phenylketonuria treat w special diet Inheritance Patterns that do not follow chromosomal theory Genomic Imprinting o Imprint Methylated allele silences gene o In gametes imprints are erased and reset according to sex of individual Organelle DNA o Mitochondria chloroplasts other plastids carry their own circular DNA o Inherited from mother