Concept explainers
The following is a portion of a protein: met-trp-tyr-arg-gly-pro-thr-Various mutant forms of this protein have been recovered. Using the normal and mutant sequences, determine the DNA and mRNA sequences that code for this portion of the protein, and explain each of the mutations.
- a. met-trp-
- b. met-cys-ile-val-val-leu-gln-
- c. met-trp-tyr-arg-ser-pro-thr-
- d. met-trp-tyr-arg-gly-ala-val-ile-ser-pro-thr-
a.

To determine: The DNA and mRNA sequences that code for this normal protein “met-trp-tyr-arg-gly-pro-thr” and explain the mutation in “met-trp”.
Introduction: The proteins are coded from triplet codons. There are 64 triplet codons, which code for 20 amino acids in which initiation and stop codons are also included. The initiation codons allow the mRNA to transcribe the DNA template while stop codons restrict the translation.
Explanation of Solution
The possible triplet codons for the normal protein “met-trp-tyr-arg-gly-pro-thr” are as follows:
Met | Trp | Tyr | Arg | Gly | Pro | Thr |
AUG | UGG | UAU | AGA | GGU | CCU | ACU |
UAC | AGG | GGC | CCC | ACC | ||
GGA | CCA | ACA | ||||
GGG | CCG | ACG |
These are the possible triplet codons for “met-trp-tyr-arg-gly-pro-thr” protein. Any mutation in the above sequences may lead to mutation.
The first mutation occurred and formed “met-trp” protein. Possibly, the mutation occurred at ‘tyr’, which resulted in the termination. The termination is caused by a stop codon. The possible triplet codons after mutation in “met-trp” are :
Met | Trp | Stop codons |
AUG | UGG | UAA |
UAG |
In the original sequence, tyrosine is present. However in mutated sequences, stop codons are formed, which shorten the polypeptide to Trp.
b.

To determine: The DNA and mRNA sequences that code for this normal protein “met-trp-tyr-arg-gly-pro-thr” and explain the mutation in “met-cys-ile-val-val-leu-gln”.
Introduction: The proteins are coded from triplet codons. There are 64 triplet codons which code for 20 amino acids in which initiation and stop codons are also included. The initiation codon allows the mRNA to transcribe the DNA template; whereas, stop codons restrict the translation.
Explanation of Solution
The possible triplet codons for the normal protein “met-trp-tyr-arg-gly-pro-thr” are as follows:
Met | Trp | Tyr | Arg | Gly | Pro | Thr |
AUG | UGG | UAU | AGA | GGU | CCU | ACU |
UAC | AGG | GGC | CCC | ACC | ||
GGA | CCA | ACA | ||||
GGG | CCG | ACG |
These are the possible triplet codons for “met-trp-tyr-arg-gly-pro-thr” protein. Any mutation in the above sequences may lead to mutation.
The second mutation occurred and formed “met-cys-ile-val-val-leu-gln” protein. Possibly the point mutation occurred which caused changes in the reading frame. The triplet codons of the mutated protein “met-cys-ile-val-val-leu-gln” are :
Met | Cys | Ile | Val | Val | Leu | Gln |
AUG | UGU | AUA | GUG | GUC | CUA | ACU |
GUG | ACC | |||||
ACA | ||||||
ACG |
The highlighted codons are mutated. The single place deletion or insertion may arise this type of situation where the complete sequence is changed.
c.

To determine: The DNA and mRNA sequences that code for this normal protein “met-trp-tyr-arg-gly-pro-thr” and explain the mutation in “met-trp-tyr-arg-ser-pro-thr”.
Introduction: The proteins are coded from triplet codons. There are 64 triplet codons which code for 20 amino acids in which initiation and stop codons are also included. The initiation codon allows the mRNA to transcribe the DNA template; whereas, the stop codons restrict the translation.
Explanation of Solution
The possible triplet codons for the normal protein “met-trp-tyr-arg-gly-pro-thr” are as follows:
Met | Trp | Tyr | Arg | Gly | Pro | Thr |
AUG | UGG | UAU | AGA | GGU | CCU | ACU |
UAC | AGG | GGC | CCC | ACC | ||
GGA | CCA | ACA | ||||
GGG | CCG | ACG |
These are the possible triplet codons for “met-trp-tyr-arg-gly-pro-thr” protein. Any mutation in the above sequences may lead to mutation.
The third mutation occurred and formed “met-trp-tyr-arg-ser-pro-thr” protein. Possibly the frameshift mutation occurred, which caused changes in the reading frame. The triplet codons of the mutated protein “met-trp-tyr-arg-ser-pro-thr” are :
Met | Trp | Tyr | Arg | Ser | Pro | Thr |
AUG | UGG | UAU | AGA | AGU | CCU | ACU |
UAC | AGG | CCC | ACC | |||
CCA | ACA | |||||
CCG | ACG |
Here, the only codon for glycine is completely changed. The single frame is inserted and deleted from the same place.
d.

To determine: The DNA and mRNA sequences that code for this normal protein “met-trp-tyr-arg-gly-pro-thr” and explain the mutation in “met-trp-tyr-arg-gly-ala-val-ile-ser-pro-thr-”.
Introduction: The proteins are coded from triplet codons. There are 64 triplet codons, which code for 20 amino acids in which initiation and stop codons are also included. The initiation codon allows the mRNA to transcribe the DNA template; whereas, the stop codons restrict the translation.
Explanation of Solution
The possible triplet codons for the normal protein “met-trp-tyr-arg-gly-pro-thr” are as follows:
Met | Trp | Tyr | Arg | Gly | Pro | Thr |
AUG | UGG | UAU | AGA | GGU | CCU | ACU |
UAC | AGG | GGC | CCC | ACC | ||
GGA | CCA | ACA | ||||
GGG | CCG | ACG |
These are the possible triplet codons for “met-trp-tyr-arg-gly-pro-thr” protein. Any mutation in the above sequences may lead to mutation.
The second mutation occurred and formed “met-trp-tyr-arg-gly-ala-val-ile-ser-pro-thr-” this protein. This is a type of mutation where the reading frame is shifted because this protein is relatively larger than the normal protein.
Hence, frame insertion is a possible way due to which the protein is completely changed.
Want to see more full solutions like this?
Chapter 9 Solutions
Human Heredity: Principles and Issues
- This question has multiple parts (A, B & C), and under the subject of Nutrition. Thank you!arrow_forwardCalculate the CFU/ml of a urine sample if 138 E. coli colonies were counted on a Nutrient Agar Plate when0.5 mls were plated on the NA plate from a 10-9 dilution tube. You must highlight and express your answerin scientific notatioarrow_forwardDon't copy off the other answer if there is anyarrow_forward
- Use the following information to answer the question(s) below. Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. Survival (%) 100- 80- 60- 40- 20- 0+ 1.9 T 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Log SVL (mm) 19) Examine the figure above. What type of selection for body size appears to be occurring in these marine iguanas? A) directional selection B) stabilizing selection C) disruptive selection D) You cannot determine the type of selection from the above information. 3arrow_forward24) Use the following information to answer the question below. Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. The dominant allele (T) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined (see table) and used to determine the actual allele frequencies in the population. TT 0.49 Tt 0.42 tt 0.09 Refer to the table above. Is this population in Hardy-Weinberg equilibrium? A) Yes. C) No; there are more homozygotes than expected. B) No; there are more heterozygotes than expected. D) It is impossible to tell.arrow_forward30) A B CDEFG Refer to the accompanying figure. Which of the following forms a monophyletic group? A) A, B, C, and D B) C and D C) D, E, and F D) E, F, and Garrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage LearningBiology Today and Tomorrow without Physiology (Mi...BiologyISBN:9781305117396Author:Cecie Starr, Christine Evers, Lisa StarrPublisher:Cengage LearningBiology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage LearningBiology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStax





