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. Mutation Description of Mutation Phenotype _ mr-1 Nonsense mutation in codon 829 Delayed-receiver mr-2 Missense mutation in codon 52 Delayed-receiver mr-3 Deletion of nucleotides 83–150 Delayed-receiver mr-4 Missense mutation in codon 192 Insensitive mr-5 Deletion of nucleotides 83–93 Insensitive 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!)

Key Concepts

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 in organisms.

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 mindreader gene. The severity of the phenotype often correlates with the type and location of the mutation within the gene, 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 phenotype. Recessive traits require two copies of the mutated gene to manifest, while dominant traits can be expressed with just one copy. In the case of the Betazoids, the recessive mutations in the mr gene lead to the delayed-receiver and insensitive phenotypes, illustrating how the inheritance pattern affects the expression of mind-reading abilities.