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Nucleic Acids and Protein Synthesis
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I. DNA = deoxyribonucleic acid A. Contains Genes = specific locations on DNA. 1.Genes specify proteins and traits (eye color, disease, etc)
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DNA is bundled into structures called chromosomes. If the DNA in a person was stretched out it would reach to the sun and back 600 times. It is an extremely long molecule that coils really tight.
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B. The Structure of DNA 1.Rosalind Franklin and Maurice Wilkins a)Produced X-ray diffraction photograph of DNA. b)Showed that: DNA is a double helix.
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2.James Watson and Francis Crick (1953) a)Used Franklin’s info to build DNA model b)Model= double helix of repeating nucleotide monomers
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` 2003 1953
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c. Nucleotides have three parts: 1)Deoxyribose Sugar 2)Phosphate Group 3)Nitrogen Base (4 kinds) Purines = Adenine (A) & Guanine (G) Pyrimidines = Thymine (T) & Cytosine (C)
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How do the nitrogen bases bind?
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d.Sugar-phosphate molecules on outside of ladder; paired bases on inside. e.Purines paired to pyrimidines. 1) A is hydrogen-bonded to T 2) G is hydrogen-bonded to C f. Watson and Crick - Nobel Prize in 1954 for their model of DNA.
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Stop End of day 1
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II. DNA Replication = process of duplicating a molecule of DNA A.Begins at a specific sequence of nucleotides B.DNA is unzipped by DNA Helicase enzyme. C.Helicase breaks the hydrogen bonds between nitrogen bases. D.Free floating nucleotides bind with complementary bases.
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II. DNA Replication = process of duplicating a molecule of DNA E. DNA polymerase enzyme catalyzes the bonding of sugar and phosphates F. Results in 2 new strands of DNA G. Each new DNA molecule has one old and one new strand (semi-conservative replication) H. Special Enzymes (DNA polymerase) “proofread” and repair any mistakes I. If repairs are not made, the mutations may cause cancer.
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I. Replication Errors Do Occur 1.Ability to mutate is requirement for genetic material. 2.Only one error per billion nucleotides.
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J. The newly synthesized strand always forms from 5’ to 3’.
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Animation of DNA Replication http://207.207.4.198/pub/flash/24/menu.sw fhttp://207.207.4.198/pub/flash/24/menu.sw f ~ 15 minutes
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STOP End of day 2
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III. Ribonucleic Acid (RNA) = makes proteins A.DNA ultimately determines amino acid sequence of proteins. B.DNA molecule cannot directly control the sequence of amino acids. C.DNA is restricted to nucleus. D.Go-between is ribonucleic acid (RNA).
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E.The Structure of RNA 1.Polymer of nucleotides (ribose sugar, Nitrogen base, PO 4 group 2. Unlike DNA, RNA : a) Single-stranded b) Contains the sugar ribose c) Contains the nitrogen base uracil instead of thymine. No “T” in RNA A-U
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F.There are three major classes of RNA. 1.Messenger RNA (mRNA)- takes a message from DNA in nucleus to ribosomes in cytoplasm. 2.Ribosomal RNA (rRNA)- and proteins make up ribosomes where proteins are synthesized. 3.Transfer RNA (tRNA)- transfers a particular amino acid to a ribosome.
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IV. Central Dogma of Molecular Biology A.DNA undergoes transcription to mRNA B.mRNA undergoes translation to a protein.
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V. Transcription =process in which mRNA is made according to the sequence of bases in DNA A.Occurs in the nucleus. B.Begins when RNA polymerase (enzyme) binds to a DNA molecule. (Unzips the DNA) C.Complementary RNA nucleotides pair with DNA nucleotides. D.RNA polymerase joins the RNA nucleotides together. E.Terminator sequence causes RNA polymerase to stop. F. DNA strands rejoin.
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VI. Translation = assembling proteins from “info” encoded in mRNA
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A.Takes place in cytoplasm. B.One language (nucleic acids) is translated into another language (protein). C.How Genes Code for Amino Acids 1.DNA serves as a template to build RNA 2.mRNA contains the genetic code in the form of codons.
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3.Codons a)3 sequential nucleotide bases of mRNA. (4 3 =64) b)Each codes for an amino acid. c)There are 64 triplets to code for 20 amino acids. d)The Code Is Universal 1)AUG is universal start codon. 2)There are three stop codons.
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D.Ribosome attaches to a start codon(AUG). E.tRNA transfers Amino Acids to the ribosome. 1.tRNA is a single- stranded ribonucleic acid that doubles back on itself to create a cloverleaf structure. 2.At one end it binds to amino acid; at other end it has an anticodon that binds to mRNA codon. 3.Brings the correct amino acid to the codon.
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4.Ribosome moves to next codon and a new tRNA brings next amino acid. 5.A peptide bond is formed between amino acids. 6.Process continues until ribosomes hits a stop codon. 7.Polypeptide (protein) is formed.
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