Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

11. Translation

The Genetic Code

Genetics

11. Translation

The Genetic Code

Previous problemNext problem

2:29 minutes

Problem 29b

Textbook Question

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.
_
Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr
Mutant 1: Met-Trp
Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr
Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-Hi
_
Use this information to answer the following questions:
For each mutant protein, determine the specific ribonucleotide change that led to its synthesis.

Verified step by step guidance

Step 1: Understand the wild-type amino acid sequence and the corresponding codons. Recall that each amino acid is encoded by a set of three ribonucleotides (a codon) in the mRNA, which is transcribed from the DNA sequence.

Step 2: Compare the mutant amino acid sequences to the wild-type sequence to identify where changes occur. For Mutant 1, note that the sequence is truncated after the second amino acid; for Mutant 2, observe the substitution of 'His' for 'Tyr' at the third position; for Mutant 3, note the completely different sequence starting from the second amino acid.

Step 3: For each mutant, determine the type of mutation that could cause the observed change: a nonsense mutation (introducing a stop codon) for truncation, a missense mutation (single amino acid substitution), or a frameshift mutation (altering the reading frame and thus the entire downstream sequence).

Step 4: Use the genetic code table to identify the specific codons for the wild-type and mutant amino acids at the positions where changes occur. Then, deduce the single ribonucleotide change(s) in the mRNA codon that would convert the wild-type codon into the mutant codon.

Step 5: Translate the mRNA codon changes back to the DNA sequence changes by replacing uracil (U) with thymine (T), thus identifying the specific ribonucleotide (or nucleotide) substitution, insertion, or deletion in the DNA that led to the mutant protein synthesis.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Genetic Code and Codon-Amino Acid Relationship

The genetic code consists of nucleotide triplets called codons, each specifying a particular amino acid. Understanding how codons translate into amino acids is essential to link changes in nucleotide sequences to alterations in protein sequences. This relationship allows prediction of nucleotide mutations based on observed amino acid substitutions.

Types of Mutations and Their Effects on Protein Sequence

Mutations such as nonsense, missense, and frameshift mutations alter the nucleotide sequence, impacting the resulting protein. Nonsense mutations introduce premature stop codons, truncating proteins; missense mutations change one amino acid; frameshifts alter the reading frame, drastically changing downstream amino acids. Recognizing these helps infer nucleotide changes from protein differences.

Translation Termination and Its Impact on Protein Length

Translation stops when a stop codon (UAA, UAG, UGA) is encountered, resulting in protein termination. Mutations that create premature stop codons produce shorter proteins, as seen in truncated mutants. Understanding stop codons and their role in ending translation is crucial to explain why some mutant proteins are shorter than the wild-type.

Watch next

Master The Genetic Code with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Textbook Question

Recombinant human insulin (made by inserting human DNA encoding insulin into E. coli) is one of the most widely used recombinant pharmaceutical products in the world. What segments of the human insulin gene are used to create recombinant bacteria that produce human insulin?

506

views

Textbook Question

Explain why it is not feasible to insert the entire human insulin gene into E. coli and anticipate the production of insulin.

335

views

Textbook Question

A research scientist is interested in producing human insulin in the bacterial species E. coli. Will the genetic code allow the production of human proteins from bacterial cells? Explain why or why not.

516

views

Textbook Question

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

__________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met -Cys-Ile-Val-Val-Val-Gln-His

______________________________________________

Use this information to answer the following questions:

The wild-type RNA consists of nine triplets. What is the role of the ninth triplet?

397

views

Textbook Question

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

___________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met -Cys-Ile-Val-Val-Val-Gln-His

___________________________________________________

Use this information to answer the following questions:

Another mutation (mutant 4) is isolated. Its amino acid sequence is unchanged from the wild type, but the mutant cells produce abnormally low amounts of the wild-type proteins. As specifically as you can, predict where this mutation exists in the gene.

1050

views

Textbook Question

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

___________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-Hi

___________________________________________________

Use this information to answer the following questions:

Of the first eight wild-type triplets, which, if any, can you determine specifically from an analysis of the mutant proteins? In each case, explain why or why not.

478

views

Textbook Question

A DNA sequence encoding a five-amino acid polypeptide is given below.

...ACGGCAAGATCCCACCCTAATCAGACCGTACCATTCACCTCCT...

...TGCCGTTCTAGGGTGGGATTAGTCTGGCATGGTAAGTGGAGGA...

What is the function of the Shine–Dalgarno sequence?

441

views

Textbook Question

A DNA sequence encoding a five-amino acid polypeptide is given below.

...ACGGCAAGATCCCACCCTAATCAGACCGTACCATTCACCTCCT...