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Nucleic Acids and Protein Synthesis I. DNA (Deoxyribonucleic Acid) Structure of DNA A. Organic compound made of nucleotides - What makes a nucleotide? (3 parts) - Sugar - Deoxyribose - Phosphate group - Nitrogen base (4 kinds) - adenine, guanine, cytosine and thymine (A,G,C,T) Nucleotide of a DNA molecule B. Watson and Crick -1953 (N.P. 1962) 1. Credited with the Double Helix Model - Spiral staircase or Twisted ladder 2. Maurice Wilkins worked with them too Who’s that lady? Rosalind Franklin C. Nitrogen Base Pairing – A, C, G, T always pair in a certain way Adenine – Thymine Cytosine – Guanine * Hydrogen bonds hold them together II. DNA Replication A. Copying DNA – DNA strand unwinds and the nucleotide chains separate (unzip) – Enzyme helps new DNA chains form by using nucleotides floating around in the nucleus – Occur in many spots along the chain – Produces two new exact copies of the original DNA strand B. Mutations – Mistakes in the replication process are rare and certain enzymes proofread and correct most errors. (1 per 1 billion escape detection) – Mutations can also be caused by chemicals, ultraviolet rays and other agents RNA Ribonucleic Acid III. RNA - Ribonucleic Acid A. B. Structure of RNA -Nucleic acid made of nucleotides -Sugar - ribose -Uracil replaces thymine and pairs with adenine -Single strand not double -RNA is smaller than DNA Purpose of RNA - to transfer directions for making proteins from the nucleus to the ribosomes RNA and DNA C. Three types of RNA – Messenger RNA (mRNA) carries genetic information from the DNA in nucleus, to the cytoplasm – Transfer RNA (tRNA) Binds to specific amino acids – Ribosomal RNA (rRNA) Makes up the ribosomes where proteins are made D. Transcription – Process of copying DNA to RNA (forming mRNA, tRNA and rRNA) – Steps Certain sections of DNA are transcribed to RNA Starting with the starters and ending with the termination signal RNA is then used to make proteins Protein Synthesis Making Proteins IV. Protein Synthesis A. Protein Structure – Polymers made of amino acids bonded by peptide bonds – Specific sequence of amino acids makes each protein – There are 20 different amino acids that make proteins B. Genetic Code – Triplets of nucleotides (codons)in mRNA to sequence amino acids for protein synthesis C. Codons (64) – Series of 3 nucleotides of mRNA that codes for a specific amino acid Several codons code for the same amino acid 4 codons do not code for amino acids – 1 start codon (AUG) – 3 stop codons (UAA,UAG,UGA) D. Translation – – – Making Proteins from the mRNA code mRNA leaves the nucleus and moves into the cytoplasm to the ribosomes (rRNA) tRNA picks up the amino acids needed to make a specific protein in the cytoplasm by using the anticodon (complementary code) tRNA E. Protein Assembly – Once at the ribosome the anticodon end of the tRNA attaches to the mRNA and the amino acid end forms a peptide bond to the next amino acid – MAKING A PROTEIN Replication Problem Given a DNA strand with the following nucleotide sequence, what is the sequence of its complimentary strand? TACCACGTGGACT Answer: ATGGTGCACCTGA RNA Transcription Problem Given a DNA strand with the following nucleotide sequence, what is the sequence of its complimentary mRNA strand? TACCACGTGGACT Answer: AUGGUGCACCUGA Codon / Anticodon Given a mRNA strand with the following nucleotide sequence, what are the sequence (anticodons) of its complimentary tRNA strands? (HINT: RNA to RNA) AUGGUGCACCUGACU Answer: AUGGUGCACCUGA Protein Translation Given the following sequence of mRNA, what is the amino acid sequence of the resultant polypeptide? AUG GUG CAC CUG ACU Answer: Methionin(Start)-Valine-HistidineLeucine-Threonine-