G Leucine Serine Tyrosine Stop Cysteine Stop Tryptophan Leucine Proline Histidine Glutamine Arginine Phenylalanine Glycine Glutamic acid Aspartic acid Alanine Valine Arginine Serine Lysine Asparagine Threonine Methionine Isolucine A G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G U A C G C C A G C C A G A A G A G C C G A G C C A U U U U U U U U What is the amino acid sequence for the codons: GCA UAC CCC GUA? alanine tyrosine proline valine UUU UUC UUA UUG UCU UCC UCA UCG UAU UAC Animated by Jeff Christopherson
Concept Map from to to make up also called which functions to also called also called which functions to which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNA Carry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNA Ribosome Ribosomes
Transcription RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only)
Translation Messenger RNA Messenger RNA is transcribed in the nucleus. Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. mRNA Start codon Ribosome Methionine Phenylalanine tRNA Lysine Nucleus mRNA
Translation (continued) The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. mRNA Ribosome Translation direction Lysine tRNA tRNA Ribosome Growing polypeptide chain mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.
Interest Grabber continued 1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. 2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. 3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. 4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5. Did this single deletion cause much change in your protein? Explain your answer.