Biology Exam 3 o The study of what genes are how they work at a molecular level Molecular Biology Genes o Store and retrieve information o Copy information o Change over time mutations Evidence o Griffith Avery characteristics of bacteria o Hershey and Chase Worked on bacteriophages The introduction of pure DNA to bacterial cells can change the Radioactive virus experiment not what it s really called o Agitate in blender to separate phage outside the bacteria from the cells and their content o Centrifuge and measure the pellet and supernatent o Radioactive protein Pink dye 35S sulfur Radioactivity was found in the supernantent Genetic makeup not found in proteins o Radioactive DNA Blue dye Radioactivity found in pellet Genetic makeup found in DNA 32P phosphorus Viral replication enlarge to read text Nucleic Acids o DNA Deoxyribonucleic acid Linear polymer of nucleotide subunits Covalent bonds between phosphate group at 5 carbon and 3 of next nucleotide Uses oxygen as bridges Nitrogenous bases stick off backbone Double stranded Double helix Watson and Crick model Strands are held together by hydrogen bonds Antiparallel o Each strand goes in opposite ways A T C G o RNA Ribonucleic acid Single stranded A U C G o Nucleotide Sugar Phosphate group Nitrogenous base A T U C G Making nucleotide Joined together by phosphodiester bonds Nitrogenous base is connected to the 1 carbon of sugar 5 3 o Direction of synthesis Phosphate group is added to 5 carbon of sugar Complementary o Base Pairing A always pairs with T or U for RNA 2 hydrogen bonds C always pairs with G 3 hydrogen bonds o Chains have opposite polarity o Cell replicates DNA by synthesizing new strands of DNA complementary to old strands Replication o Before each cell division the DNA must be replicated so each daughter cell can get a complete genetic set o Three different theories of how DNA can be replicated Conservative new strands The two parental strands reassociate after acting as templates for Semiconservative The two strands of the parental molecule separate and each functions as a template for synthesis of a new complementary strand The correct one Dispersive Each strand of both daughter molecules contains a mixture of old and newly synthesized DNA o Begins at origins on chromosomes and proceeds bidirectionally away from the origin o Initiation Helicase binds to the origin and unwinds the DNA Primase attaches and makes a shorter primer RNA DNA Polymerase attaches to the primer and begins replication o DNA Polymerase Adds deoxyNTPs to 3 end of DNA 5 to 3 synthesis Requires DNA template Requires a primer for starting replication Proofreader Detects missing nucleotide base and replaces it DNA Polymerase III Does most of DNA replication Goes along strand and attaches complementary nucleotides DNA Polymerase I completes lagging strand synthesis and removing the RNA primers puts DNA in its place o Both strands of DNA are replicated simultaneously at each replication fork Leading strand is replicated continuously Lagging strand is replicated in small places o Primase and DNA polymerase III jump forward after each lagging strand piece is made Messelson Stahl Experiment o E Coli was grown in media containing heavy salts o The cells were then transferred to a medium containing light salts o DNA was isolated from the cells after each round of replication DNA molecules were separated based on density by centrifusion DNA repair o DNA polymerase makes an error every 105 106 bases copied o Radiation and certain chemicals can damage DNA o DNA restriction enzymes find unpaired bases and damaged bases Cut them out from one side of double helix base DNA Polymerase I fills in the correct Uses DNA base pairing Prokaryote chromosomes o 4 000 000 base pairs long o Single circular DNA Eukaryote chromosomes o Linear chromosomes o 3 000 000 000 base pairs o Packed by histone proteins o Chromatin DNA plus histone proteins Transcription o mRNA molecule is constructed from gene s nucleotide sequence o RNA polymerase binds to promoter one Makes RNA molecule using complementary base pairing with one strand Sequence of bases at the beginning of each gene Transcriptions factors bind to promoter o Twists DNA open of DNA o RNA polymerase Synthesizes 5 3 Does not need primer Joins ribonucleotides Makes single strand of RNA molecule Binds to transcription factors then to DNA o RNA processing Blocks further addition of subunits by binding cap protein to free mRNA Eukaryotes only Done in nucleus Capping end of RNA Needed for translation Additional polyA tail Needed for translation Protects RNA from any enzymes trying to break it down Internal pieces of mRNA that were cut out Introns Extrons Remainder of mRNA present Spliced together o Done by spliceosomes o Bind to intron exon borders o Cut out introns o Join exons contains info in its nucleotide sequence the codes for a specific protein product Types of RNA o All coded for in DNA o Messenger RNA mRNA Translated o Ribosomal RNA o Transfer RNA tRNA Used in translation Translation rRNA structural components of the ribosomes o mRNA s base sequence is used to put together the correct sequence of amino acids that the genes code for o Ribosome reads mRNA three bases at a time codons Joins correct amino acids together o The Genetic Code Each three base codon specifies one amino acid Redundant Multiple codons for more than one amino acid One start codon Three stop codons AUG UAA UAG UGA All organisms use the same genetic code o Involves the three types of RNA tRNA Bring amino acids to ribosome Base pair with codon Amino acid is attached to the 3 end and polypeptide Three bases at the top of the anticodon loop base pair with the codon Requires ATP Two subunits rRNA o Large and Small subunits Three major active sites Where tRNAs enter o A site o P site o E site Where tRNAs exit Where tRNAs holding the peptide chain is located mRNA o Four steps tRNA charging reaction Uses up ATP Chain initiation tRNA with a particular anticodon is joined with the correct amino acid Small subunit and tRNA methionine bind the mRNA Large subunit binds tRNA met base pairs with the start codon in the mRNA tRNA met is in P site Chain elongation Charges tRNA enters A site Peptide forms mRNA is shifted three bases o Leaves new tRNA in P site o Old tRNA is ejected Chain termination Involves release factors that mimic tRNA Mutations o Change in DNA base sequence o Source of inherited disorders and most cancers o Source of all genetic variability
View Full Document
Unlocking...