Ch 10 Nucleic Acid And Protein Synthesis

Chapter 10: Nucleic Acid and Protein Synthesis Structure of DNA: • Nucleotide: Phosphate – 5 Carbon Sugar – Nitrogenous Base • 4 Different Bases: Adenine, Thymine, Cytosine, and Guanine o Purines: Adenine and Guanine o Pyrimidines: Cytosine and Thymine • Base-Pairing Rules: Adenine bonds to Thymine / Cytosine bonds to Guanine DNA Replication: 1. The enzyme, helicase, unzips (breaks weak hydrogen bonds) the DNA molecule 2. The DNA unzips completely, forming two separate strands 3. DNA polymerase begins to base pair the nucleotides on each template 4. Two completely identical chromatids are produced RNA • • •

vs. DNA Different sugars: ribose (RNA) / deoxyribose (no O2)(DNA) Chain: single chain (RNA) / two chains (DNA) RNA uses the base Uracil in place of thymine

Transcription: • RNA Synthesis (DNA copied) • The process by which a molecule of DNA is copied into a complementary strand of RNA • RNA polymerase attaches to DNA separates two strands and synthesizes mRNA o Special “start” and “termination” signals are recognized by RNA polymerase Structure of RNA: • mRNA: Messenger RNA; “mediates” between the DNA and ribosomes in the cytoplasm o Single, straight chain • rRNA: Ribosomal RNA; makes up the ribosomes in the cytoplasm o Wrapped around itself • tRNA: Transfer RNA; carries amino acids that combine to form a protein o Anticodon on one side and amino acid on the other Translation: • The decoding of mRNA into a polypeptide chain (protein) • 4 nucleotides arranged in “triplets” (codons) o Each codon specifies the amino acid

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TRNA has two sides for attachment o One side (anticodon) that bonds to codon on mRNA o One particular amino acid on the other end The anticodon of tRNA pairs with the mRNA codon, bringing an amino acid to the growing polypeptide chain o The stop codon tells the mRNA when to end the chain