1. For the middle region of a particular polypeptide chain, the wild-type amino
ID: 216216 • Letter: 1
Question
1. For the middle region of a particular polypeptide chain, the wild-type amino acid sequence and the amino acid sequence of three mutants were determined, as shown in the following table. For each mutant, indicate what type of change has occurred to the DNA. Determine whether the change is a base pair substitution (indicate either transition or transversion, and either missense or nonsense) or a frameshift mutation, and in which codon the mutation occurred. (Refer to the Genetic Code in Table 12-7, page 222) (3 points) Codons 1 2 3 4 5 6 7 8 9 Wild-Type Phe Leu Pro Thr Val Thr Thr Arg Trp Mutant A Phe Leu His His Gly Asp Asp Thr Val Mutant B Phe Leu Pro Thr Met Thr Thr Arg Trp Mutant C Phe Pro Pro Arg 2. Products resulting from somatic mutations, such as the navel orange and the Delicious apple, have become widespread in citrus groves and apple orchards. However, traits resulting from somatic mutations are seldom maintained in animals. Why? Why is the maintenance of somatic mutations common in plants but not in animals? (2 points)Explanation / Answer
1) While comparing it with wild type and Mutation A there are many differences in the amino acids which are coding for different codons and that is why there is a change. This change is from the third amino acid from Proline to Histidine, Threonine to Histidine, Valine to Glycine, Threonine to Aspartic acid, Threonine to again Aspartic acid, Arginine to Threonine, Tryptophan to Arginine. This long chain in change of codons could be due to frame shift mutation. Not just a gene but a whole frame has got shifted. A mutation caused by addition or deletion of codons in the base pairs in the DNA of a gene. This results in the transformation of the genetic code and a change in the reading frame from the position of the mutation to the end of the gene. In the second mutation that is Mutant B while comparing it with Wild type the changes occurred only in the 5th amino acid that is a change from Valine to Methionine is due to a small change in one base pair in these codons which lead to this change in the whole amino acid. This change or mutation is called single point mutation or Missense mutation where a single base pair changes in the DNA of the gene. Here in this case Valine (CUG) to Methionine (AUG), so the change is visible enough to judge it is Missense mutation. In Mutant C when compared with Wild type there are 2 amino acids being changes and there is no further amino acids present. In Mutant C Leucine had changed to Proline where in again there is only single base pair change in them. Leucine (CUU) and Proline (CCU), Threonine (ACG/ACA) to Arginine (AGA/AGG) the mutation observed here is also the same.
2) Somatic cells give rise to all Non germline tissues. Mutations in the somatic cells are called somatic mutations because they do not occur in the cells that give rise to gametes, the mutation is not passes along to the next generation by sexual means. Somatic mutations occur in non reproductive cells, to maintain this mutation the individual containing the mutation must be cloned, one example of such clone is the navel orange and red delicious apples. They were grafted on to the normal trees and grown. In this way the mutation was proliferated and maintained to produce effective products. In animals somatic mutations are rare because they do not occur in the right genome in the right cell at the right time. Most of the time the mutation goes undetected because the cell that is mutated dies and it is replaced by the time it can ever be noticed, also the mutation does not get passed on to their offspirngs.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.