Chapter 15Pgs 286-194 and 297-302Pages 303-304 1-3,5,71-22 chromosomes are autosomes23 is the sex chromosomesSex linked genes- examples in mammalso SRY Gene Sex-determining Region of Y chromosomeo DAX gene DosAge sensitive gene on X chromosomeSex-linked traits/disorders- due to gene on a sex chromosome (X or Y)- Often Recessiveo Female (XX) – carrier if heterozygous or affected if homozygouso Male (XY)—Hemizygous, affected if have gene- Ex: color blindness, hemophilia (Fig 15.7)Discovery Timeline1860’s - Mendel’s law of inheritance1870-1890s- Physical process of mitosis/meiosis discovered1902- Sutto and Boveri proposeo Chromosomal theory of inheritanceo Mendelian genes have specific loci (positions) on chromosomes1928- Griffith recognized a principle (Process) - Proposes “Heritable substance transforms cells”- Transformation: change the genotype and phenotype due to assimiliation of external DNA- Pathogenic straino Living S (smooth) Straino Kills the mouse- Non Pathogenic Straino Living R (rough) cellso Mouse healthy- Heat-killed S cells (control)o Mouse healthy- Mixture of heat-killed S cells and living R cellso Mouse dieso Living S cells are in the mouse1944- Avery, McCarty, MacLeod experimentso Only DNA transforms cellso Living R + S-cell protein Mouse healthyo Living R + S-cell RNA Mouse Healthyo Living R + S-cell DNA Mouse DIES Only DNA transforms bacteria 1950- Erwin Chargraffo # adenines = # thymineso # guanines = # cytosines1952- Hershey and Chase (Figure 16-4-1) o Bacteria and Bacteria Phageso Soaked in Radioactive Sulfur Proteins have sulfur No radioactivity was foundo 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- 1953o 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 traitsGenetic Variation-Recombination of Genes1) Independent assortment are combines unlinked genesTest CrossHeterozygous and a homozygous RecessiveIf Testcross results in:- Parental Type—Greater than 50% offspring phenotypes- Recombinant Type—much less than 50% offspring phenotypes new combosThen- Linked genes: genes located on the same chromosome, “tend” to be inherited together, but not always due to crossing overAbnoraml Chromosome Number Nondisjuction-When homologous chromosomes or sister chromatids do NOT separate1) Aneuploidy- offspring w/ abnormal # of a particular chromosome (monosomy, trisomy)a. Down Syndrome (Tisomy 21b. Klinefelter Syndrom (XXY)c. Turner Syndrome (XO)2) Polyploidy- offspring w/ more than 2 complete chromosome setsa. Triploidy (3N), Tetraploid (4N), etc. Testing for Genetic Disorders1) Identify Carriersa. Use in vitro fertilization and screen embryos2) Fetal Testing (Fig. 14-18)a. Amniocentesisb. Chlorionic Villus Samplingc. Ultrasound3) Newborn Screeninga. PKU (phenylketonuria)-treat w/ special diet Inheritance Patterns that do not follow chromosomal theory- Genomic Imprintingo Imprint—Methylated allele, “silences” geneo In gametes, imprints are “erased” and reset according to sex of individual - Organelle DNAo Mitochondria, chloroplasts, other plastids carry their own circular DNAo Inherited from