BSC 2010 Exam 3 Study Guide Chapter 5 uracil guanine DNA contains hereditary information that can be passed on A always pairs with T G always pairs with C Nitrogenous bases are called bases due to their ability to take up a H from a solution pyrimidine one 6 ring carbon contains cytosine thymine and 2 types Purines one 6 ring with a 5 ring attached contains adenine and Phosphate groups provide a way for nucleotides to come together and form polynucleotides the phosphate group only attaches to the 5 carbon this creates a backbone consisting of only sugars and phosphates NOT nitrogenous bases These backbones end up having a 5 carbon end that is attached to a phosphate and a 3 carbon end that is attached to a hydroxyl group RNA vs DNA Exists as single polynucleotide chain two polynucleotide chain varies in shape due to single chain forms a double helix bases A U and G C bases A T and G C since DNA has two complementary strands its possible to make two identical copies of itself Chapter 16 Frederick Griffen was the one that led the breakthrough of experiments accomplished this while studying bacteria and how viruses infected them he mixed a pathogenic strand and a harmless strand together in his experiment Led to harmless strand developing traits of the pathogenic strand Double Helix two outer sugar phosphate backbone with nitrogenous bases hydrogen bonds form b t these nitrogenous bases These bonds can easily break which always the double helix to split and replicate itself This results in each daughter strand having an old strand from the parent DNA and a newly made strand Strands are in a 3 5 and 5 3 formation which results in them being antiparallel Replication parent DNA contains two complimentary strands that can be unraveled and used as templates for replication new DNA contain a strand from old DNA and a newly developed strand this process is known as semi conservative model Origins of replication where replication starts found where short stretches of DNA have a certain sequence Proteins recognize this sequence and attach to the DNA which causes the two stands to separate and form a replication bubble Here is where replication takes place until fully copied Leading Strand DNA strand synthesized along template toward replication fork elongates continuously unlike lagging strand Lagging Strand discontinuously synthesized as a series of fragments called Okazaki Fragments synthesized away from the replication fork Helicases are enzymes that untwist the double helix Topoisomerase relieves the strain in the double helix caused by the untwisting of the double helix RNA primer needed to start replication since DNA enzymes can only add nucleotides to the end of an existing chain Primer gets synthesized by primase Primase starts a complementary RNA chain from a single RNA nucleotide and uses parental DNA strand as a template How does Okazaki Fragment get added to DNA DNA polymerase I replaces RNA nucleotides with DNA ones Then DNA ligase joins the fragments into a continuous strand Linear Chromosome replication can only add nucleotides to the 3 end causes replications to produce shorter strands Telomeres help with this issue by attaching themselves to the ends to stop this shortening process telomeres consist of multiple repetitions of short nucleotide sequence Circular Chromosome replication does not have ends the shortening process never happens Chromatin formed when Eukaryotic DNA combines with large amount of protein Histones are responsible for the levels of DNA packing in chromatin H2A H2B H3 H4 important in the 2nd level of packing H1 is involved in further levels of packing Vocabulary 1 DNA Replication the process by which a DNA molecule is copied also called DNA synthesis 2 Transformation 1 the conversion of a normal animal cell to a cancerous cell 2 A change in genotype and phenotype due to the assimilation of external DNA by a cell When the external DNA is from a member of a different species transformation results in horizontal gene transfer 3 Bacteriophage a virus that infects bacteria 4 Virus an infectious particle incapable of replication outside of a cell consisting of an RNA or DNA genome surrounded by a protein coat capsid and for some viruses a membranous envelope 5 Double Helix the form of native DNA referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape a 6 Antiparallel referring to the arrangement of the sugar phosphate backbones in a DNA double helix they run in opposite 5 3 directions 7 Semiconservative model type of DNA replication in which the replicated double helix consists of one old strand derived from the parental molecule and one newly made strand a 8 Origin of replication site where the replication of a DNA molecule begins consisting of a specific sequence of nucleotides 9 Replication fork A Y shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized 10 Primer a short stretch of RNA with a free 3 end bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication 11 DNA polymerase an enzyme that catalyzes the elongation of new DNA for example at a replication fork by the addition of nucleotides to the 3 end of an existing chain 12 Okazaki fragments a short segment of DNA synthesized away from the replication for on a template strand during DNA replication Many such segments are joined together to make up the lagging strand of newly synthesized DNA 13 DNA ligase a linking enzyme essential for new DNA replication catalyzed the covalent bonding of the 3 end of one DNA fragment such as an Okazaki fragment to the 5 end of another DNA fragment such as a growing DNA chain 14 Mismatch repair the cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides 15 Nuclease an enzyme that cuts DNA or RNA either removing one or a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides 16 Telomere the tandem repetitive DNA at the end of a eukaryotic 17 Nucleotide a non membrane bounded region in a prokaryotic cell where chromosome s DNA molecule the DNA is concentrated 18 Chromatin the complex of DNA and proteins that makes up eukaryotic chromosomes When the cell is not dividing chromatin exists in its dispersed form as a mass of very long thin fibers that are not visible with a light microscope 19 Heterochromatin eukaryotic
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