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

17. Mutation, Repair, and Recombination

Types of Mutations

Genetics

17. Mutation, Repair, and Recombination

Types of Mutations

Previous problemNext problem

1:42 minutes

Problem 28

Textbook Question

Among Betazoids in the world of Star Trek®, the ability to read minds is under the control of a gene called mindreader (abbreviated mr). Most Betazoids can read minds, but rare recessive mutations in the mr gene result in two alternative phenotypes: delayed-receivers and insensitives. Delayed-receivers have some mind-reading ability but perform the task much more slowly than normal Betazoids. Insensitives cannot read minds at all. Betazoid genes do not have introns, so the gene only contains coding DNA. It is 3332 nucleotides in length, and Betazoids use a four-letter genetic code.
The following table shows some data from five unrelated mr mutations.

For each mutation, provide a plausible explanation for why it gives rise to its associated phenotype and not to the other phenotype. For example, hypothesize why the mr-1 nonsense mutation in codon 829 gives rise to the milder delayed-receiver phenotype rather than the more severe insensitive phenotype. Then repeat this type of analysis for the other mutations. (More than one explanation is possible, so be creative within plausible bounds!)

Verified step by step guidance

Understand the genetic code and the impact of mutations: The mr gene is 3332 nucleotides long, and Betazoids use a four-letter genetic code. Each codon consists of three nucleotides, and mutations can alter the resulting protein's structure and function. The phenotypes (delayed-receiver and insensitive) are determined by the severity of the mutation's impact on the protein's function.

Analyze mr-1 (Nonsense mutation in codon 829): A nonsense mutation introduces a premature stop codon, truncating the protein. Since codon 829 is relatively late in the gene, the majority of the protein is still synthesized. This partial protein may retain some functionality, leading to the delayed-receiver phenotype rather than the complete loss of function seen in insensitives.

Analyze mr-2 (Missense mutation in codon 52): A missense mutation changes one amino acid in the protein. Since codon 52 is early in the gene, this mutation likely alters the protein's structure but does not completely disrupt its function. This partial functionality could explain the delayed-receiver phenotype.

Analyze mr-3 (Deletion of nucleotides 83–150): This deletion removes a segment of the gene, potentially causing a frameshift mutation. However, if the deletion does not disrupt critical functional domains of the protein, the resulting protein may still retain partial activity, leading to the delayed-receiver phenotype.

Analyze mr-4 and mr-5 (Missense mutation in codon 192 and deletion of nucleotides 83–93): The missense mutation in codon 192 likely disrupts a critical functional domain of the protein, leading to the insensitive phenotype. Similarly, the deletion of nucleotides 83–93 may cause a frameshift or remove essential amino acids, resulting in a complete loss of function and the insensitive phenotype.

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.

Gene Mutations

Gene mutations are alterations in the DNA sequence of a gene, which can affect the function of the protein produced. These mutations can be classified into several types, including nonsense mutations, which introduce a premature stop codon, and missense mutations, which result in a different amino acid being incorporated into the protein. Understanding how these mutations impact protein function is crucial for explaining the resulting phenotypes.

Phenotype Expression

Phenotype expression refers to the observable traits or characteristics of an organism, which result from the interaction of its genotype with the environment. In the context of the Betazoids, the phenotypes of delayed-receivers and insensitives arise from specific mutations in the mr gene. The severity of the phenotype often correlates with the type and extent of the mutation, influencing the protein's functionality.

Recessive vs. Dominant Traits

In genetics, traits can be classified as dominant or recessive based on their expression in the presence of alleles. Recessive traits, like the insensitivity phenotype in Betazoids, require two copies of the mutated allele to be expressed, while dominant traits can manifest with just one copy. This distinction is essential for understanding why certain mutations lead to milder or more severe phenotypes based on their genetic inheritance patterns.

Watch next

Master Point Mutations with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Textbook Question

Assume that a mutation affects the gene for each of the following eukaryotic RNA polymerases. Match each mutation with the possible effects from the list provided. More than one effect is possible for each mutation.

Ribosomal RNA is not processed.

386

views

Textbook Question

Some tRNA is not synthesized.

450

views

Textbook Question

Some rRNA is not synthesized.

395

views

Textbook Question

Pre-mRNA does not have introns removed.

365

views

Textbook Question

Some pre-mRNA is not synthesized.

393

views

Textbook Question

Most organisms display a circadian rhythm, a cycling of biological processes that is roughly synchronized with day length (e.g., jet lag occurs in humans when rapid movement between time zones causes established circadian rhythms to be out of synch with daylight hours). In Drosophila, pupae eclose (emerge as adults after metamorphosis) at dawn.

In each case, how would you clone the genes you identified by mutation?

487

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:

Using the genetic coding dictionary, predict the type of mutation that led to each altered protein.

918

views

Textbook Question

Shown below are two homologous lengths of the alpha and beta chains of human hemoglobin. Consult a genetic code dictionary, and determine how many amino acid substitutions may have occurred as a result of a single nucleotide substitution. For any that cannot occur as a result of a single change, determine the minimal mutational distance.

Alpha: ala val ala his val asp asp met pro

Beta: gly leu ala his leu asp asn leu lys

445

views

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap