NOTES: DNA to Protein There are three types of RNA: a. Messenger RNA (mRNA) – transfers the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm. b. Transfer RNA (tRNA) – transfers amino acids to the ribosomes for addition to a protein chain. c. Ribosomal RNA (rRNA) – makes up part of the ribosomes for protein synthesis (“protein synthesis” = making a protein) How does DNA tell the cell which protein to make? A. It uses a nucleic acid called RNA. B. RNA is a little different than DNA: 1. RNA has the sugar ribose instead of deoxyribose. 2. RNA is only a single strand. 3. RNA contains the nitrogenous base uracil instead of thymine. * Uracil bonds with adenine. Steps in the process of protein synthesis: Transcription: 1. The helicase… “unzips” part of the double helix. Transcription: 2. There is a “start” and “stop” sequence in the DNA to tell the mRNA where to start and stop. UGA = stop AUG = start UAA = stop UAG = stop Transcription: 3. RNA nucleotides pair up to DNA nitrogenous bases and…bond in a chain 4. The mRNA travels to the ribosome, where the protein will be assembled. (Note: DNA never leaves the nucleus!) Steps in the process of protein synthesis: Translation: 5. When mRNA binds to the ribosome,… production of a protein begins Steps in the process of protein synthesis: Translation: 6. The mRNA code is read and converted into a specific amino acid sequence in a protein chain 7. This process continues until a functional protein is made. This means the protein has a purpose, such as a hormone, enzyme, or a structural part of a cell membrane. Summing Up Protein Synthesis 4. A strand of amino acids make a protein. 3. The tRNA leaves to get more amino acids. 2. The tRNA brings the appropriate amino acids to the mRNA in the ribosome. 1. RNA transcribes the original DNA strand.