Changes to the Genetic Code Reporting Category 2 Mechanisms of Genetics Station 8 Changes to the Genetic Code

Essential Question-Bell Ringer Humans have approximately 75,000 to 100,000 genes in a typical cell. A single gene contains about 10,000 nitrogen base pairs. How is it possible for a single mutation to one of these base pairs to cause a life-threatening condition? Journal

Essential Question answer: Nitrogen base combinations code for amino acids, which produce proteins. If a mutation to one of the base pairs affected a protein that was vital to the functioning of a crucial organ or system, this mutation would cause the organ or system to fail. Journal

Pre-Review Question During the process of protein synthesis, a section of the DNA molecule is copied into which other molecule? Nucleic acid Cytoplasmic DNA Messenger RNA Transfer RNA

Pre-Review Question In messenger RNA, each codon specifies a particular: Nucleotide Purine Amino acid Pyrimidine

Pre-Review Question True True or False Any change in the genetic sequence (DNA) that affects the genetic information is referred to as a mutation. True

Pre-Review Question Type of mutation that takes place when a base codon is changed but both code for the same amino acid: Silent mutation Transition mutation Transversion Deletion

Lab Activities You will now go to the lab and complete the activities for todays topics…

Genetic Code Wheel

AUG CCA ACA GUG AGA UUA CAG AAA UCG UAA Write and answer the question in your journal (Include the DNA sequences) 1. Using the mRNA Genetic Code chart, determine the name of the amino acid each codon represents. AUG CCA ACA GUG AGA UUA CAG AAA UCG UAA Start, proline, theorine, valine, arganine, leucine, glutamine, lysine, serine, stop. This will serve as your original strand. 2. What does this chain of amino acids represent? A polypeptide chain or a protein strand.

AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA Write and answer the question in your journal (Include the DNA sequences) 3. Some genetic mutations are caused by changes in the bases of some codons. Compare the two sequences below and compare them to the original sequence. Can you identify which codon was changed and what the new amino acid will be? AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA 11

AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA Answer AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA Uracil has been replaced with cytosine This will change the amino acid from valine to alanine. AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA Alanine has been replaced with guanine. However, this still codes for the same amino acide. This is known as a silent mutation. 12

AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A Write and answer the question in your journal (Include the DNA sequences) 4. If an additional base is added it it called a frameshift. Compare the original strand to the strand below and find the insertion. How many amino acids would be affected? AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A 13

AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A Write and answer the question in your journal (Include the DNA sequences) 4. If an additional base is added it it called a frameshift. Compare the original strand to the strand below and find the insertion. How many amino acids would be affected? AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A Start, proline, theorine, cysteine, glutamic acid, isoleucine, threonine, glutamic acid, isoleucine, valine, nothing. 14

5. What is the significance of this frame-shift mutation for the structure of the protein? After the mutation, 7 of the 10 codons now code for a different amino acid than the original sequence did. In addition, a single adenine (A) base ends the strand. This frame-shift mutation will cause massive changes in the types of protein produced by the new strand.

What I need to remember…. • Mutations are changes in DNA that can be inherited. • Certain codons are responsible for starting the production of a protein, and other codons stop the process. • Mutations occur when bases are added or deleted and when segments of DNA are missing. • Not all mutations are harmful—some are very beneficial.

Post Review Question What type of point mutation is illustrated in the table below? Substitution Silent Deletion Insertion Original Strand Mutated Strand DNA TAC GTA CGG TAA TGC GTA CGG TAA mRNA AUG CUA GCC AUU ACG CAU GCC AUU Amino acid Met His Ala Iso Thr His Ala Iso

Post Review Question Identify the following mutation: Translocation Deletion Inversion Duplication

Post Review Question Identify the following mutation: Translocation Deletion Inversion Duplication