Investigation: DNA, Proteins, and Mutations 7th Hour

Investigation: DNA, Proteins, and Mutations Below are two partial sequences of DNA bases (shown for only one strand of DNA) Sequence 1 is from a human and sequence 2 is from a cow. In both humans and cows, this sequence is part of a set of instructions for controlling a bodily function. In this case, the sequence contains the gene to make the protein insulin. Insulin is necessary for the uptake of sugar from the blood. Without insulin, a person cannot digest sugars the same way others can, and they have a disease called diabetes.-Using the DNA sequence, make a complementary RNA strand from both the human and the cow. Write the RNA directly below the DNA strand (remember to substitute U's for T's in RNA).-Use the codon table in your book to determine what amino acids are assembled to make the insulin protein in both the cow and the human. Write your amino acid chain directly below the RNA sequence. DNA 3' to 5' CCA TAG CAC GTT ACA ACG TGA AGG AAA RNA GGU AUC GUG CAA UGU UGC ACU UCC UUU Amino Acid Gly Ile Val Gln Cys Cys Thr Ser Phe Cow DNA CCA TAG CAT GTT ACA ACG CGA AGG GAC RNA GGU AUC GUA CAA UGU UGC GCU UCC CUG Amino Acid Gly Ile Val Gln Cys Cys Ala Ser Leu Amino Acid Chart Analysis 1. Compare the DNA Sequence and find any single base that is different in the cow and human sequences. How many bases are different? 82. Examine the amino acids produced and find any amino acids that are different in the two sequences. How many are there? 4 3. Could two humans (or two cows) have some differences in their DNA sequences for insulin, yet still make the exact same insulin proteins? Explain. 4. Examine the codon chart and list all of the codons that code for the amino acid leucine. Mutations Diabetes is a disease characterized by the inability to break down sugars. Often a person with diabetes has a defective DNA sequence that codes for the making of the insulin protein. This mutation is called a POINT MUTATION because only one base is affected. When the amino acid in a sequence has been changed, the shape of the protein changes and can become less functional (or not function at all.) 5. Suppose a person has a mutation in their DNA, and the first triplet for the gene coding for insulin is T A T(instead of C C A). Determine what amino acid the new DNA triplet codes for. Will this person be diabetic? Explain 6. A SILENT MUTATION occurs when the nucleotide changes, but the resulting amino acid is the same. The protein that is made from this new DNA will have no functional difference from the original. What if a mutation occurred in the human insulin gene and the first triplet was changed to CCG? Is this a silent mutation? Explain how you know. A FRAMESHIFT MUTATION occurs when a base is added (or removed) from a DNA sequence. 7. Determine the amino acid chain coded for by the following sequence. Suppose a mutation occurs where another A is added after the first codon. What would the new sequence of amino acids be? (make sure to put a space after each codon and amino acid) Normal DNA: TGG AGT CGA GGTNormal RNA: ACC UCA GCU CCAAmino Acids: Thr Ser Ala ProMutant DNA: TGG AAG TCG AGG TMutant RNA: ACC UUC AGC UCC AAmino Acids: Thr Phe Ser Ser 8. Why are frameshift mutations likely to cause more problems than a point mutation? 9. A NONSENSE MUTATION occurs when a codon is changed to a STOP codon. Many proteins are thousands of amino acids in length. At the end of the gene, the cell reaches the stop codon. If a codon is changed to STOP, the building of the amino acid terminates and the protein is incomplete. Why would a Nonsense mutation be less damaging if it occurred at the end of the gene rather than the beginning? Gene Sequences Across Species DNA sequences are often used to determine relationships between organisms. DNA sequences that code for a particular gene can vary widely. Organisms that are closely related will have sequences that are similar. Below is a list of sequences for a few organisms:Human: CCA TAG CAC CTAPig: CCA TGG AAA CGAChimpanzee: CCA TAA CAC CTACricket: CCT AAA GGG ACG10. Based on the sequences, which two organisms are most closely related? 11. An unknown organism is found in the forest, and the gene is sequenced, and found to be C C A T G G A A T C G A , what kind of animal do you think this is? 12. Explain why some mutations are more harmful than others.