1. Protein Synthesis
Chapter 11

2. RNA Genes are coded DNA instructions that control protein production
First, DNA must be copied to RNA
RNA structure: identical to DNA except:
Sugar = Ribose (not deoxyribose)
N base = C, G, A, and Uracil (U) (replaces thymine)
Single-stranded

3. Types of RNA Main function RNA: to assemble amino acids into proteins
Messenger RNA (mRNA): carry copies of instructions to make proteins from DNA in nucleus → cytoplasm (ribosomes)
Ribosomal RNA (rRNA): help make ribosomes
Transfer RNA (tRNA): transfers amino acids to ribosomes for protein assembly

4. Transcription
Transcription: process by which portion of DNA is copied to complementary RNA sequence inside nucleus
Requires RNA polymerase (an enzyme)
Binds to DNA and separates strands
Uses DNA strand as template to make RNA complement

5. The Genetic Code “Language” of mRNA instructions
Read 3 letters at a time, called a codon, that specify a single amino acid
64 total possible codons → 20 amino acids
Example:
UCGCAG = UCG + CAG
Serine + Glutamine… → Protein (polypeptide)

6. Translation
Translation: the decoding of an mRNA sequence into amino acids on ribosomes
Begins at AUG (“start” codon)
Codons of mRNA match up with Anticodons of complementary tRNA
Translation continues until a “stop” codon is read (UAA, UAG, UGA)
Result is chain of new proteins!!

7. Protein Assembly
Amino acids connect with peptide bonds to form proteins (“polypeptides”)
Proper synthesis of proteins is essential to organism survival
Proteins are enzymes – control most chemical reactions
i.e.: photosynthesis, cellular respiration, etc.
“By coding for proteins, DNA holds the key to life”
Protein Synthesis