chap 11 dna fall '08

chap 11 dna fall '08 - Today we will Today Lecture today on...

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Unformatted text preview: Today we will Today Lecture today on Lecture – Genetics quick look – How DNA discovered – DNA structure – How DNA replicates Chapter 11 Chapter DNA The molecule of heredity heredity The Heredity defined is ‘the passing of traits the Heredity from one generation to the next’ from Genetics Defined: the study of heredity Defined: the Genetics Is the study of heredity Is – Heredity is ‘the passing of traits from one generation to the next’ Done by reproduction –Via gametes (egg-sperm) or Via spores spores DNA The molecule of heredity Genetics Is the study of heredity Is – Heredity is ‘the passing of traits from one generation to the next’ Done by reproduction – Via gametes (egg-sperm) or spores Prokaryotes have __?___ DNA Eukaryotes have ___?___ DNA – Have 2 types of cells Genetics Diploid cells Diploid Haploid cells Genetics Diploid cells Diploid Haploid cells Have two homologous sets of chromosomes Have one set of chromosome 1n 2n A C B V g F K l A L L V f C B g K l k k A c B V G F Triploid Triploid olyploid Polyploid Genetics (cont.) Genetics Chromosomes = chromatin = DNA+protein A unit (segment) of DNA that governs a particular trait = gene gene – Genes come in 2 forms (alleles) Dominant allele Recessive allele – Homozygous – Heterozygous Genetics (cont.) Genetics Chromosomes = chromatin = DNA+protein A unit (segment) of DNA that governs a particular trait = gene – Genes come in 2 forms (alleles) Dominant allele Recessive allele – Homozygous – Heterozygous b b A A D d Genetics (cont.) Genetics Chromosomes = chromatin = DNA+protein A unit (segment) of DNA that governs a particular trait = gene – Genes come in 2 forms (alleles) Dominant allele g Recessive allele – Homozygous E – Heterozygous Locus Linked Genotype Phenotype Phenotype M g E m DNA “the molecule of heredity” DNA Deoxyribonucleic acid – Same structure in all except C & M – Is the Is “blueprint” of ALL life Directs what happens in each cell of an each organism organism ?? Is HOW ?? Defin Defin ed ed as?? as?? So How was the link between genes, heredity, and DNA discovered How History Fredrick Griffith-1920s-bacterial pneumon TRANSFORMATION TRANSFORMATION SIMILATION OF EXTERNAL DNA into a cell’ SIMILATION DNA thereby modifying its genotype thereby resulting resulting in a phenotype change in treptococcus neumoniae shows that living R bacteria had been transformed into pathogenic S bacteria by an unknown heritable substance from the dead S cells Transformation. This experiment was a turning point in genetics because researchers suspected that the substance causing transformation might be the long sought after molecule of heredity But what was the substance?????? This experiment was a turning point in genetics because researchers suspected that the substance causing transformation might be the long sought after molecule of heredity Fredrick Griffith-1920s-bacterial pneumonia Fredrick Oswald Avery 1944 Oswald Hershey & Chase 1952 Showed DNA was genetic material Linked to genes Sulfur and Sulfur Phosphorous DNA Gross Structure DNA Monomer+Monomer+……. >>>> Polymer How bonded? How made? How broken? Nucleotide+nucleotide+… >>>>> Nucleic Nucleotide+nucleotide+… Acid Acid Can also be referred to as a polynucleotide Can polynucleotide DNA and RNA formed this way Phosphate group base base DNA is composed of same 4 nucleotides in ALL organisms nucleotides T A C G Except ? RNA RNA Function – Serves as a helper to DNA to bring about Serves protein synthesis protein RNA RNA Before 1940 knew ATCG present Erwin Chargaff 1940s Erwin – Analyzed DNA from many organisms – Experiments yielded Rules Experiments Rules The amount of A,T,G,C in DNA varies from species to The species species But found equal amts of A & T or G & C Y? –Had no Had idea why idea prompted researchers to discover That paired bases can be in any o That 140 million base pairs = 4 Know what it is made of Know Know the ratio of building blocks different organisms have different base But how structured? But If DNA is molecule of heredity how does it DNA Store information Vary between species DNA criteria criteria Replicate Undergo change (mutate) Only destructure Only knows DNA Structure DNA ay ray diffraction studies - 1950s DNA molecule long, thin and 2nm in diameter Has repeating subunits Rosalind franklin “we have discovered the secret of life” Utterance made in Eagle Pub, March 7, 1953 by Crick Duh! Duh! Sounds good to me me crick on wats –Had no idea why ANSWER: “Complementary Base Pairing” Watson & Crick 1953 Watson nuceleotide They were thinkers guessed Hydrogen bonds = ladder-like construction Double helix & opposite strand directions Complementary base pairs Same width (big-little) So a DNA molecule DNA Has two polynucleotide strands strands Each strand forming a Each backbone of sugar and phosphate units covalently bonded held together by hydrogen bonds at their antiparallel antiparallel DEOXYRIBOSE DEOXYRIBOSE vs RIBOSE DNA + histone proteins form nucleosomes nucleosomes nucleosome subunits form chromatin chromatin tightly coiled chromatin form chromosome chromosome an organism’s chromosomes = genome genome What is it about the DNA’s structure that allows it to be the blueprint? blueprint? or How can it hold all the info How necessary to ‘control’ life? necessary Done by the sequence of nucleotide subunits sequence HAT ORDER THE BASES OF THE NUCLEOTIDES ARE LINED U Done by the sequence of nucleotide subunits sequence a stretch of DNA that is only 10 nucleotides long can have more than one million possible sequences of the four bases Therefore DNA can encode a staggering amount of information ME IS 3 BILLLLLION NUCLEOTI ME HAS SOME 20,000 GENES OPPED INTO 23 CHROMOSOME DNA Replication DNA Replication permits genetic info to be Replication passed from generation to generation passed Why important ????? – How it’s done ensures accurate copying of genetic information copying DNA Replication DNA DNA replication happens DNA before cell division before Cell life cycle availability of raw materials and the timing of replica nsures DNA replicates only once prior to cell divisio nsures once DNA Replication DNA Replication happens before cell division – Raw materials & timing of replication ensures DNA replicated only once Raw once prior to cell division prior Replication produces a duplicated chromosome of 2 Replication identical sister chromatids sister centromer e Listen hard DNA Replication DNA Is “ semiconser vative r eplication” Is Raw materi als DNA helicase helicase An enzyme Pulls DNA double Pulls helix apart helix DNA h An e elicase nzy Pulls DNA me helix double apar t DNA polymerase An enzyme Matches the base on strand to the free nucleotide base AND Daughter chromosomes DNA polymerase DNA An enzyme Matches the base on strand to the free nucleotide base fre AND miconservative Replication = ew + 1 old strand Catalyzes the Catalyzes covalent bond between adjacent nucleotides nucleotides Daughter chromosomes Breaks Breaks complimentary base pairs at their hydrogen bonds bonds duplicating chromosome will have many bub Moves toward “free sugar” end of the Moves “free DNA strand DNA Follows the helicase Semiconservative replication Free nucleotides Free To “free sugar” To “free end end erase # 2 moves to right, helicase moves to the left leaving unmatched strand of erase ll ill this gap, DNA polymerase #3 ‘lands’ on the unpaired strand and begins what?? iiven that ven And so on And Review testable Helicase does? Helicase T/F only one bubble per chromosome DNA Polymerase does? In what direction does it travel? ? Continuous vs ?discontinuous Why DNA polymerase #3 Ligase does? DNA Polymerase #4 – why? Perficton a musk Perficton Replication occurs at @ 700 nucleotides/sec generates 1 error every 10,000 base pairs generates But Only 1 error in 1,000,000,000 found Why? Proofreading polymerases during and after synthesis synthesis Mistakes do happen Mistakes No such thing as an error free DNA – 10,000 base pairs/cell/day lost – Many base pairs not needed 3 billion base pairs Only 10,000 maybe 30,000 genes – Severely damaged May die May not function as efficiently May become cancer am n e am n e am n e am n e ameam n eam n amn e en am n e am n n e am n e eam n mame am n e em n n a eam n am en am e ee am nam nam am n e eam nn e am n am n am n e e e am n e am n eam n mn e e ...
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