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12–3 RNA and Protein Synthesis Copyright Pearson Prentice Hall What is RNA? Ribonucleic acid.. It too like DNA is a nucleic acid! RNA contains codes for making proteins (body tissues such as muscle, hair, enzymes, etc..) Copyright Pearson Prentice Hall Let’s compare RNA to DNA DNA RNA Deoxyribose Sugar Ribose A, T, G, C A, U, G, C Double Nitrogenous Bases Strands Nucleus Location Anywhere in cell Single 3 Types of RNA Messenger mRNA Ribosomal rRNA Transfer tRNA Copyright Pearson Prentice Hall Messenger RNA (mRNA) Makes a copy of DNA. Every 3 letters on an mRNA is a codon (we will get there, don’t worry ) ribosomal RNA (rRNA) are what ribosomes are made of. Types of RNA transfer RNA (tRNA) Carry or “transfer” amino acids to the ribosome. Copyright Pearson Prentice Hall The Genetic Code The genetic code is the “language” of mRNA instructions. The code is written using four “letters” (the bases: A, U, C, and G). Copyright Pearson Prentice Hall The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid. Copyright Pearson Prentice Hall For Example… Consider the following RNA sequence: UCGCACGGU This sequence would be read 3 bases at a time as: UCG-CAC-GGU The codons represent the different amino acids: Serine-Histidine-Glycine Copyright Pearson Prentice Hall Because there are 4 different bases…. There are 64 possible 3-base codons (4 x 4 x 4 = 64). Look at Figure 12-17 in your book on pg. 303. This shows all 64 possible codons of the genetic code. See mRNA Codon/Amino Acid Chart Handout!!! Copyright Pearson Prentice Hall Looking at Figure 1217…. As you can see, some amino acids can be specified by more than one codon. For example, 6 different codons specify the amino acid Leucine and 6 others specify Arginine. There is also one codon, AUG, that can either specify methionine or serve as the initiation, or “start” codon for protein synthesis. Copyright Pearson Prentice Hall See if you can figure this out… What amino acid is specified by CAU? What is the codon for tryptophan? What are two possible codons for glutamine? What amino acid is usually the first amino acid of a protein? How do you know? Copyright Pearson Prentice Hall Video Time So… What the heck is protein synthesis? Copyright Pearson Prentice Hall Step 1 of Protein Synthesis 1. Transcription: mRNA is transcribed from DNA in the nucleus and released into the cytoplasm Copyright Pearson Prentice Hall Step 2 of Protein Synthesis 2.Translation: mRNA attaches to a ribosome and an amino acid is brought by a tRNA to the mRNA. Copyright Pearson Prentice Hall It works like an assembly line Lysine Translation direction mRNA Copyright Pearson Prentice Hall tRNA Ribosome -The process continues until the ribosome reaches a stop codon. -It then releases the newly formed polypeptide (which creates a protein) and the mRNA molecule completes the process of translation. Polypeptide Ribosome tRNA Copyright Pearson Prentice Hall mRNA Why do we care about what protein synthesis does? Proteins determine eye color, hair color, etc... Copyright Pearson Prentice Hall RNA Editing Some DNA within a gene is not needed to produce a protein. These areas are called introns. The DNA sequences that code for proteins are called exons. Copyright Pearson Prentice Hall 12–3 Click to Launch: Continue to: - or - Slide 22 of 39 End Show Copyright Pearson Prentice Hall 12–3 A base that is present in RNA but NOT in DNA is a. thymine. b. uracil. c. cytosine. d. adenine. Slide 23 of 39 End Show Copyright Pearson Prentice Hall 12–3 The nucleic acid responsible for bringing individual amino acids to the ribosome is a. transfer RNA. b. DNA. c. messenger RNA. d. ribosomal RNA. Slide 24 of 39 End Show Copyright Pearson Prentice Hall 12–3 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the a. intron. b. exon. c. promoter. d. codon. Slide 25 of 39 End Show Copyright Pearson Prentice Hall 12–3 A codon typically carries sufficient information to specify a(an) a. single base pair in RNA. b. single amino acid. c. entire protein. d. single base pair in DNA. Slide 26 of 39 End Show Copyright Pearson Prentice Hall