Unit 3 Study Guide Chapter 5 Structure Function of Large Biological Molecules DNA is the material inherited from one generation to the next within chromosomes Chromosomes are made of Proteins DNA Fredrick Griffith created an experiment using bacterium to see if DNA or Proteins are molecules of heredity Used S cells Pathogenic Strain R cells Non Pathogenic Strain Injects S cells into mouse mouse dies Injects R cells into mouse mouse lives Takes S cells heat kills them injects into mouse mouse lives Heat kills S cells mixes them with living R cells mouse dies Something was passed from killed S cells to living R cells Converting R cells into S cells This is called Transformation change in genotype phenotype due to assimilation of foreign DNA In Griffith s experiment DNA was transformed not Protein Heat disrupts hydrogen bonds within macromolecules Secondary Tertiary structure of proteins are held together by hydrogen bonds More evidence for DNA being the molecule of heredity came from studying viruses bacteriophages Viruses are made up of DNA Proteins like chromosomes DNA was labeled with P32 phosphorus DNA has no sulfur Protein was labeled with S35 sulfur Proteins have no phosphorus Phages infected bacterial cells while marked When centrifuged radioactive DNA was in the bottom pellet meaning DNA was molecule of heredity Erwin Chargaff studied the composition of DNA and came up with two rules The base composition of DNA varies between species In any species the number of A T bases are equal and the number of C G bases are equal Rosalind Franklin used X ray crystallographic images to find DNA has a double helix structure Watson Crick found DNA s backbones run antiparallel subunits run in opposite directions DNA Deoxyribonucleic acid 3 end is a hydroxyl group OH 5 end is a phosphate group PO4 Deoxy means one less oxygen oxygen is missing from 2 carbon Double stranded ds consist of many genes Double strand produces a double helix around imaginary axis RNA Ribonucleic Acid Contains no T bases instead it uses U Single stranded ss dsRNA is very rare Each gene in DNA produces separate RNA molecules Nucleoside nitrogenous base sugar Nitrogenous bases A G are Purines larger T C U are Pyrimidines smaller Base pairs require one Purine one Pyrimidines Nucleotide nucleoside phosphate group Chapter 16 The Molecular Basis of Inheritance DNA is the only biological molecule that can copy itself DNA contains more information than RNA Protein DNA follows semi conservative replication the new replicated strand is half old DNA half new DNA Meselson Franklin came up with a model supporting semi conservative model Labeled original DNA with heavy nitrogen N15 then transferred it into a medium with light nitrogen N14 and finally centrifuged Resulted in one band composed of 50 old DNA 50 new DNA and one band of all new DNA Each cell has a specific amount of DNA and they do not tolerate more or less DNA Cells form Diploid cells a cell with two copies of chromosomes instead of one in preparation for division Cells only replicate their DNA in preparation for cell division Initiation when DNA begins to separate into separate strands to replicate Begins at the origin of replication where Helicase unzips DNA s hydrogen bonds Single Strand Binding Proteins help keep DNA strands from rejoining stabilizes strands Primase adds a short RNA primer to both ssDNA to begin replication Eukaryotic cells have no mechanism for adding DNA nucleotides to a naked ssDNA As long as there is a portion that is double stranded DNA can be added RNA or DNA As DNA is unzipped Topoisomerase travels ahead of the replication fork making supercoils to counter act the supercoils induced by unwinding the DNA DNA polymerase adds new DNA nucleotides to the growing DNA strands DNA polymerase can only add nucleotides to the 3 end New strand that is continuous from 5 to 3 direction is called the leading strand needs one primer Lagging strands are created to complete the rest of the strand needs multiple primers Primase assembles new primers Lagging strands are synthesized by DNA polymerase III Forms a series of segments called Okazaki fragments DNA polymerase I removes RNA primers fills gap with DNA nucleotides DNA ligase joins the 3 end of lagging strand to the 5 end of the other DNA molecule Termination DNA replication is stopped Prokaryotes have termination sites Eukaryotic cells don t Telomeres repetitive DNA sequences at the end of eukaryotic chromosomes that postpone the erosion of molecules Telomerase enzyme that catalyzes production of Telomeres found in germ cells to maintain length in offspring In regular somatic cells the length of Telomeres shortens as organism gets older Both DNA Polymerase I III have 3 to 5 exonuclease activity that can remove wrong nucleotides as soon as they are added Polymerase I can remove in ahead behind itself Polymerase III can only in front Humans add nucleotides at 50 per second Bacteria add nucleotides at 500 per second Histomes proteins associated with DNA to build chromosomes positively charged to bond to negative DNA Chromatin chromosome structure Hetrochromatin Euchromatin Tightly packed histomes DNA aka nucleosomes at resting state No replication or transcription loosely packed nucleosomes during replication or transcription Chapter 17 From Gene to Protein DNA is responsible for inheritance enzyme production and function Minimal medium has the lowest amount of nutrients required for growth After being exposed to X rays damaged cells because they won t grow on minimal medium after exposer leads to non functional enzymes The mutant cells only grow if you provide arginine to minimal medium RNA is the bridge from genes to proteins Prokaryotes Translation can begin before transcription has finished due to lack of nucleus No processing of RNA before translation Translation in ribosomes plasma membrane or free cytoplasm Translation Transcription are completely separate RNA processed in nucleus must translocate from nucleus to cytoplasm Translation in ribosomes free ribosomes nuclear envelope or rough ER Eukaryotes Transcription first stage of gene expression RNA polymerase makes RNA polymers adds RNA nucleotides to the 3 end as it grows RNA is made complementary to DNA template use same bases except uracil instead of tymine Promoters places where RNA polymerase attaches piece of DNA that s transcribed is called transcription unit Transcription factors bind to DNA forming a transcription initiation factor
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