BIO 151 1st Edition Lecture 9Outline of Last Lecture 1. Electrochemical effects2. Nucleic acids3. Active transport with transporters (pumps) work against the diffusion gradient4. Heredity, genes, and DNA5. Darwin, Evolution, and Heredity (1859)6. Why did we take so long to figure out heredity?7. Is all life "pre-formed?"8. Inheritance of traits "acquired" by parents from experience, environment?9. Mid-1800s10. Mendel's (1861) rules for sexual inheritance of "genes"11. What is a gene?Outline of Current Lecture 1. But what was a gene?2. Bacteria growing in a dish (bacterial "culture") can be transformed (Griffith 1920-30s)3. Virus DNA infects cell4. Hershey-Chase (1952)5. 1947: Chargaff's Analysis of DNA6. DNA is it. What's the structure?7. DNA double helix8. Nucleotides covalently linked into "strand" that can contain any sequence of nucleotides ("bases) in any order9. Nucleotides ("bases") on one strand hydrogen bond to "complementary" nucleotides on other strand = base pairing10. Two "strands" of helix run in opposite directions11. Accurate replication is important because...Current Lecture - 2/9/15But what was a gene?- genes on chromosomes- chromosomes contain DNA and proteins- most thought genes were proteins. Why?1. Many different proteins with different activities.2. DNA had about equal concentrations of 4 nucleotides (A,C,G,T)1) Bacteria growing in dish (bacterial "culture") can be transformed (Griffith 1920-30s)- smoth (S) pneumonia bacteria kill mice, rough (R) do not- growing R cells with ground up (dead) S cells transforms R to S- smooth had cell wall around them - deadly, protected from immune system- after transformation, S is stably inherited- take S cell extract, remove proteins (add proteinase), RNA (add RNAase), lipids, or carbohydrates- extract still transformed R to S (Avery, 1944)1. Hypothesis - "testable"-repeatableThese 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. Occam's Razor - simplest hypothesis wins-transformation of bacteria depends on DNA-treat with enzyme that removes DNA (DNAase), transformation is blocked2) Virus DNA infects cells:- virus - not a cell- particle that contains proteins and nucleic acid- makes infected cells produce more virus- bacteriophage (phage) virus infects bacteriaHershey-Chase (1952): - grow virus with nutrients that radioactively label either proteins (35S in amino acids methionine and cysteine) or DNA (35P in phosphates)- virus has protein coat, head, DNA, tail core, tail sheath, and tail fibers- virus protein labeled with 35S stays outside cells, can be washed off- virus DA labeled with 35P gets inside cells, cannot be washed off1947: Chargaff's analysis of DNA:- levels of the 4 nucleotides (A,C,G,T) not identical!- varied from species to species- Ex. 30.9%A, 29.4% T, 19.9% G, 19.8% C- Chargaff's "rule" -% A = % T% C = % GDNA is it. What's the structure?:- California - Linus Pauling (discoverer of the protein alpha helix)- London - Maurice Williams +/- Rosalind Franklin (experts on X-ray crystallography)- Cambridge, UK - James Watson and Francis Crick- Wilkins, Franklin, and co-workers doing X-ray crystallography on DNA-make solid DNA crystal, shine X-rays, scatter pattern gives structural info.- Watson, Crick saw Franklin's (unpublished data) - Franklin, writing manuscripts Feb/March 1953- Watson-Crick paper published side-by-side with Franklin-Wilkins data paperDNA double helix:- sugar phosphates on outside- nitrogenous bases on inside- hydrogen bond between nitrogenous bases model:1) Nucleotides covalently linked into "strand" that can contain any sequence of nucleotides ("bases") in any order-thymine and cytosine (pyrimidines)-adenine and guanine (purines)2) Nucletides ("bases") on one strand hydrogen bonds to "complementary" nucleotides on other strand = base pairing-T pairs with A-C pairs with G (opposite ends of the alphabet match, middle 2 letters match)-constrained by constant width of helix and pattern of hydrogen bonds-purine and pyramidine 3) Two "strands" of helix run in opposite directions-antiparallel-5' end to 3' end-all covalent bonding between phosphates-noncovalent bonding (hydrogen bonding) between 2 strands -always start nomenclature with 5' at beginning-DNA replication (copying) - one strand is "template" for making new complementary strand-start - separate strands - add matching nucleotides - ligate (link) themAccurate replication is important because...:- sequence of nucleotides contains code for making sequence of amino acids in protein- information flow of "central Dogma"- from DNA to RNA to protein- replication: used to make identical DNA - DNA used to make RNA- RNA used to make
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