EXAM 3 BIOLOGY EXAM STUDY GUIDE Chapter 5 The Structure and Function of Large Biological Molecules Nitrogenous Bases complimentary base pairing between Pyrimidines single 6 membered ring 5 Purines 6 membered ring fused to a membered ring Guanine G Adenine A Cytosine C H bonds with Thymine T in DNA H bonds with Uracil U in RNA ex 5 ATTGCA3 3 TAACGT5 Nucleotides monomer of DNA consists of 1 a nitrogenous base 2 pentose sugar and 3 one or more phosphate group H helix Nucleic Acids Deoxyribonucleic acid DNA two polynucleotides double antiparallel strands run 5 3 sugar deoxyribose 2 C is an C G A T longer than RNA Ribonucleic acid RNA single polypeptide chains carries protein info sugar ribose 2 C in an OH C G A U nucleotides form covalent bonds between the sugar of one nucleotide and the phosphate of another to form a nucleic acid Chapter 16 The Molecular Basis of Inheritance Matthew Meselson and Frankin Stahl supported the semi conservative repli cation model their experiment 1 labeled the nucleotides of the old strands with a heavy isotope of nitro gen N15 while any new nucleotides were labeled with a lighter isotope N14 2 Bacteria cultured in medium with 15N heavy isotope 3 Bacteria transferred to medium with 14N lighter isotope 4 centrifuged after first and second replication 5 results less dense at top more dense at bottom 1 initiation breaks H bonds and separates strands begins with the origin of replication DNA REPLICATION prokaryotes circular DNA 1 origin of replication eukaryotes linear DNA multiple origins of replication a replication bubble opens at the origin creates two replication forks on each end of the bubble proteins recruited for replication of DNA helicase unwinds separates the 2 strands breaks H bonds between nu single strand binding proteins stabilizes ssDNA single stranded DNA cleotides one at each replication fork keeps the strands from rejoining coiling back together keeps the strands single stranded demonstration with rope if you open DNA the rope you have tight twisting down the length of the strand rope it must release tension by coiling onto itself this is where topoisomerase comes in topoisomerase travels ahead of the replication fork in both directions as DNA is being twisted tighter and tighter it cuts the phosphate sugar back bone and reattaches it to create supercoils primase adds a RNA primer short 10 30bp piece of DNA to the naked DNA nucleo tides can not be di rectly added to single stranded DNA basis for elongation DNA polymerase cat alyzes the elongation of new DNA at a replication fork requires a primer and a DNA template strand adds nucleotides ONLY to the free 3 end moves from 5 to 3 only uses breaking exergonic and rejoining endergonic of phosphates a new strand of DNA during DNA replication 2 elongation the actual copying on DNA RNA primer must be replaced with DNA nucleotides only needed to initiate DNA Pol 1 removes the primer and fills in the gap with DNA nucleotides DNA ligase seals the gap in the sugar phosphate backbone leading strand the easy copying synthesis is continuous in the 5 to 3 di rection lagging strand the bitch its synthesized by DNA Polymerase III works in the opposite direction of the replication fork because it must run 5 to 3 primes assembles new primers synthesized in a series of Okazaki fragments DNA Pol III Okazaki fragment how are they eventually joined together to form continuos dna 3 termination prokaryotic proteins bind to the ter site on the opposite side of the origin will stop the replication fork from proceeding to wait for the other side to catch up be chopped off without negative effects to replication eukaryotic telomere DNA on the end of chromosomal DNA cap that can telomeres in somatic body cells generally shorter in older individu telomeres in germ sex cells shortening can t be tolerated they only als maintain their original length What is chromatin complex in eukaryotic chromosomes linear DNA histone proteins makes up the chromosomes needs to be tightly packed so that a lot of DNA can fit in small spaces histone proteins positively charged protein that wraps around negatively charged DNA complex is neutral histone acetylation loosens chromatin and promotes transcription histone phosphorylation loosens chromatin and promotes transcription histone methylation stops transcription DNA methylation the buzz kill addition of methyl groups to DNA bases stops transcription causes long term inactivation of genes will be carried through cell division that gene will not be expressed for the fur ther generations this is called epigenetic inheritance how does chromatin affect transcription euchromatin loosely packed chromatin transcription heterochromatin highly condensed chromatin no transcription genetic info is usually not expressed circular chromosome replication bacteria prokaryotic single DNA molecule 1 origin of replication linear chromosome replication humans eukaryotic multiple linear chromosomes multiple origins of replication on each chromosome Chapter 17 From Gene to Protein DNA RNA protein Archibald Garrod in 1902 he suggested that genes dictate phenotypes and DNA may have a role in protein production he linked genes to enzymes that catalyze specific chemical reactions experiment growth of bread mold wild type cells growing and dividing no growth mutant cells cannot grow and divide TRANSCRIPTION RNA is synthesized 5 3 chinery prokaryotic translation can begin before transcription has finished no processing of RNA before translation no nuclear envelope to separate the DNA from the rest of the cellular ma translation occurs at ribosomes plasma membrane or free eukaryotic translation is completely separate from transcription RNA is processed in the nucleus RNA translocates from the nucleus to the cytoplasm translation occurs at ribosomes free nuclear envelope or ER 1 initiation in the nucleus creating a strand of RNA from DNA to be used in protein coding later on DNA to RNA has the same base pair process as DNA to DNA except Thymine is replaced with Uracil U A not T A moter of transcription promoter signal the start of transcription extends several dozen nucleo tide pairs upstream of the start point where RNA polymerase attaches RNA polymerase builds the RNA strand complimentary to the DNA tem plate strand begins to transcribe a gene into mRNA after a certain nucleo tide sequence the promoter it binds to the promoter and begins tran scription at a nucleotide known as the start point in eukaryotes this
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