DNA can’t do it alone so it Bio NOTES: Protein Synthesis Remember… DNA contains the instructions for making proteins the sequence of nucleotides in DNA codes for proteins proteins are very important for all life’s functions DNA makes proteins through a process called protein synthesis, which occurs in the ribosome. Protein Synthesis occurs in 2 parts: part I - transcription part II - translation DNA can’t do it alone so it gets help from another nucleic acid - RNA.

What is RNA? Types of RNA mRNA – messenger RNA tRNA – transfer RNA RNA stands for ribonucleic acid It is made of ribose sugars, phosphates, and nitrogen bases RNA is single-stranded There is NO thymine in RNA – only adenine, cytosine, guanine and uracil - uracil takes the place of thymine A pairs with U C pairs with G Types of RNA mRNA – messenger RNA takes DNA information from nucleus to the ribosome tRNA – transfer RNA transfers or transports amino acids to the ribosome rRNA – ribosomal RNA used in making ribosomes

Part I: Transcription transcription = process where DNA is copied into mRNA occurs in the nucleus DNA cannot leave the nucleus but the message of DNA needs to get out of the nucleus What is the message of DNA?? the order of nucleotides that determine a specific protein mRNA can take message of DNA out of the nucleus Steps of Transcription: DNA unzips mRNA bases pair with one of the DNA strands 3. a single-stranded mRNA is made 4. mRNA leaves the nucleus 5. DNA zips back up

Part I: Transcription DNA mRNA A U triplet = 3 nucleotides on a DNA molecule triplet codon T A G C codon = 3 nucleotides on an mRNA molecule G C C G DNA (triplets) ATT CCT GAG TTC A U mRNA (codons) UAA GGA CUC AAG Each codon codes for a specific amino acid. The sequence of amino acids determines the type of protein to be made. Remember that amino acids are the monomers of proteins. All organisms use the same genetic code for amino acids and assembling proteins. That is why the genetic code is said to be universal. mRNA codon: UUG *See Genetic Code* amino acid: leucine

The Genetic Code 1. UUC Phenylalanine 2. CCC Proline 3. AGC Serine 4. UGA Stop

Part II: Translation translation = process where the cell uses information from mRNA to produce proteins occurs in the ribosomes of the cytoplasm Steps of Translation: 1. The mRNA strand attaches to a ribosome in the cytoplasm 2. tRNAs carry specific amino acids to the ribosome 3. The tRNA anticodon pairs with the correct mRNA codon 4. The ribosome slides along the mRNA to the next codon while the tRNAs bring more amino acids 5. The amino acids are joined together by peptide bonds 6. Continues until a STOP codon is reached

Part II: Translation mRNA tRNA A U codon U A codon = 3 nucleotides Start U A codon = 3 nucleotides on an mRNA molecule G C anticodon = 3 nucleotides on a tRNA molecule C anticodon G U tRNA is responsible for bringing amino acids to the ribosome. tRNA has an anticodon, which is the opposite of the mRNA codon. It is important to remember that the mRNA codon determines the amino acid, NOT the tRNA anticodon. mRNA: U U A C G A A G C U C G tRNA: A A U G C U U C G A G C amino acid: Leucine - Arginine - Serine - Serine

Complete the Following Chart: DNA: TAC AAG CTT GGG ATA CGC TAA ATT mRNA: AUG UUC GAA CCC UAU GCG AUU UAA tRNA: UAC AAG CUU GGG AUA CGC UAA AUU amino acids: Phenylalanine - Glutamic Acid - Proline - Tyrosine - Alanine - Isoleucine - Stop Start - **Remember – use the mRNA codons to determine the amino acids!!