BOLOGY 107 Lecture 25Outline of Last Lecture I. Chromosomal Basis of Inheritancea. Sex-linked traitsb. Gene linkagec. Recombination frequencyd. Errors in chromosomal inheritanceOutline of Current Lecture II. Corrections to Notes on X-linked Gene PedigreeIII. Non-Mendelian Geneticsa. Maternal imprintingb. Genetic Materialc. DNA structureCurrent LectureCorrections to Notes on X-linked Gene Pedigree1) When stating that an affected male cannot come from an affected male and that the descendents from a non-affected male are not affected are only considering that the non-affected male cannot pass the affected gene as they do not have it.Non-Mendelian Genetics2) Maternal imprintinga) Gene can be methylated in the egg or spermb) Methylated gene is replicated during mitosis after fertilizationc) Modifies the resulting phenotypei) Heterozygote will display a different phenotype depending on if the methylated gene comes from the mother or father(1) Due to X-inactivation3) Genetic Materiala) Found by Morgani) Genetic material found in a linear array along chromosomes(a) Identified as proteins and DNA, not sure which carried genesb) Griffith experimenti) Identified two bacterial strains, one that causes pneumonia and one that doesn’t(1) S strain- smooth coat, pathogenicThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.(2) R strain- rough coat, non-pathogenicii) Living cells of each strain were injected into mice as control(1) S strain mice died, R strain mice livediii) Tested heat-killed S strain injected into mice, mice livediv) Mixed heat-killed S strain and living R strain together and injected into mice, mice died(1) Extracted living S strain from the mouse, change in R strainc) Avery experimenti) Followed Griffith’s experiment ideaii) Altered by stripping away proteins, lipids, carbohydrates, and RNA from the heat-killed S strain cells to only leave DNAiii) Mixed DNA with living R cells and injected into mice, mice died(1) There was question as to if only DNA was leftd) Hershey-Chase experimenti) Used distinctive radioactive labeling of protein and DNA in bacteriophages(1) Bacteriophages are viruses that infect bacteria. They are made of DNA and proteins and transfer their genetic material into the cell while leaving a coat attached to the cellii) Labeled proteins in bacteriophage one color while labeled DNA a separate color(a) After allowing the virus to infect the cells, the cells were ran through ablender to detach cells and virus coats(b) Mixture was ran in a centrifuge to separate cells and coats(2) Viral coats were found as the supernatant and DNA was found in the cellsiii) Concluded that DNA was the genetic material4) DNA structurea) Linear polymer of nucleotidesi) Sugar backboneii) 4 possible nitrogenous bases(1) Thymine (T), adenine (A), cytosine (C), guanine (G)b) Contributing insightsi) Edwin Chargaff(1) Studied DNA composition in many species(2) Chargaff’s rules(a) The base composition of DNA (% As, Ts, Gs, and Cs) differs from species to species(b) % A always equals % T; % G = % Cii) Rosalind Franklin(1) Used X-ray diffraction(a) DNA is helical(b) DNA is double stranded(c) Phosphates are on outside(d) DNA has a minor repeat and a major repeat (individual bases and helical turns)(e) Approximate measurementsiii) Watson and Crick(1) Made first models of DNA and tried to fit Chargaff’s and Franklin’s
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