BIOL 1441 1st Edition Lecture 28 Outline of Last Lecture I. Inheritance of sex-linked genesII. Color blindnessIII. Barr BodyIV. Genetic disordersOutline of Current Lecture I. DNAII. TransformationIII. DNA replication modelCurrent LectureI. DNA-Deoxyribonucleic Acida. 1953, James Watson & Francis Crick introduced double-helix structure of DNAb. Hereditary information encoded in DNA c. Whole code- every single cell of the bodyd. DNA directs its own replicatione. DNA is the genetic materialf. Early in the 20th century, the identification of the molecules of inheritance loomed as a major challenge to biologistsg. Morgan’s group showed genes located on chromosomes, 2 components of chromosomes-DNA & protein —candidates for the genetic material (1910)h. Search for the Genetic Material:i. Protein- great heterogeneity and specificity of function, requirements for hereditary materialii. Little known about DNA- too uniform to account for multitude of specific inherited traits i. Frederick Griffith, 1928i. Worked with 2 strains of the bacteria Streptococcus pneumoniaeThese 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.1. Rough, “R” strain- harmless2. Smooth, “S” strain – pathogenicii. Why does smooth coat cause infection?1. Encapsulated, immune cells can’t detect itII. Transformationa. Change in genotype and phenotype due to uptake of foreign DNAb. Griffith doesn’t solve the questioni. Provides a cluec. Something in that smooth bacteria was inserted into the live rough bacteria transforming them into smooth bacteriad. A genetic trait was passed from one organism to anothere. Find the material responsible for transformation- find the hereditary molecule f. How does R transform to S?i. Protease  transformationii. DNase  no transformationiii. *DNA is responsible for transforming ability, NOT protein* g. Bacteriophagesi. Phages- viruses that only infect bacteria, highly specificii. Hershey & Chase, 19531. Use T2 phage- infects E. coli2. Viruses- DNA & proteiniii. Viruses infect bacteria, hijack host replication machinery to make virus proteins instead of host proteins1. Viral coat stays outside bacteria (protein)iv. What do the viruses inject into the bacteria to replicate themselves?1. DNA or protein?v. Experimental Design1. Grow T2 phage in radioactive sulfur 35Sa. Labels proteins only (no sulfur in DNA)2. Grow T2 phage in radioactive phosphorus 32Pa. Labels DNA only 3. Infect separate samples of E. colivi. Results1. Labeled protein- all in supernatanta. Pellet contained bacterial cells- no labeled protein2. Labeled DNA- all in pellet with bacteria3. Shows that DNA is transferred into bacterial cell, not protein4. DNA must be the molecule responsible for replicating- transferringgenetic informationh. Erwin Chargaff- 1947i. DNA composition varies from one species to the next1. Molecular diversity from one species to nextii. Chargaff’s Rule1. If you run an experiment and find a species of bacteria has 33% adenines, what percentage of guanine does this species have?a. 33% adenine = 33% thymine b. =66% total DNAc. 100 – 66 = 34% DNAd. 34% DNA = 17% guanine + 17% cytosinei. DNA is Genetic Material, how does it replicate itself?i. Already known that DNA is a polymer of nucleotides:1. Nitrogenous base2. Sugar3. Phosphate group4. *Structure = Functionii. Want to know how DNA confers heritability, figure out the structure.j. X-Ray Diffractioni. X-rays diffract as pass through purified fibers of DNA, producing spots andsmudgesii. Use mathematical equations to translate patterns into information about the 3D shapes of the moleculesiii. Wilkins (behind Franklin’s back) shows Watson the famous photograph 51iv. Photo 51 enabled Watson to deduce that DNA was helical & figure the width of the helix & the spacing of the nitrogenous basesv. The width suggested that the DNA molecule was made up of two strands, forming a double helixvi. Watson & Crick built models of a double helix to conform to the X-rays & chemistry of DNAvii. Franklin had concluded that there were 2 antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule’s interiork. Genetic Diversityi. Base-pairing dictates the combinations of nitrogenous bases, the sequence of nucleotides along each strand is not restrictedii. Linear sequence could be varied in countless waysiii. Each gene has a unique order (or base sequence)l. Watson, Crick, Wilkins received the Nobel Prize in medicine or physiology for their determination of the structure of DNAm. Franklin died in 1958 of ovarian cancer, she was only 37 yrs oldn. Nobel Prize can be awarded only to the living, Franklin could not be honoredIII. Replication Modela. Relationship between structure and function is manifest in the double helixb. Watson & Crick noted that the specific base pairing suggested a possible copying mechanism for genetic materialc. The Basic Principle: Base Pairing to a Template Strandi. 2 strands of DNA are complementary, each strand acts as a template for building a new strand in replicationii. In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on base-pairing