Question

Heterogeneity within a disease may manifest as a. allelic heterogeneity, in which many variants of a single gene can cause the same disease b. locus heterogeneity, in which variants in many different genes may cause the same disease c. some of the difficulties underlying genetic studies of neurodegenerative diseases d. all of the above e. none of the above

Short answer

Short answer: The correct answer is d. all of the above. This is because allelic and locus heterogeneity both exist in neurodegenerative diseases, and they complicate genetic studies by making it difficult to pinpoint the exact genetic cause or understand the specific gene-disease relationship.

Step-by-step solution

Define allelic heterogeneity

Allelic heterogeneity refers to the presence of different mutations in a single gene that can cause the same disease. In other words, multiple variants of a gene can lead to the same phenotype or disease manifestation.

Define locus heterogeneity

Locus heterogeneity refers to different genes being responsible for causing the same disease. In this scenario, mutations in multiple different genes can lead to the same phenotype or disease manifestation.

Discuss the difficulties in genetic studies of neurodegenerative diseases

Due to the presence of allelic and locus heterogeneity, genetic studies of neurodegenerative diseases can be challenging. With multiple genetic variants potentially causing the same disease, pinpointing the exact genetic cause or understanding the specific gene-disease relationship can be complex. Now that we have discussed allelic and locus heterogeneity and their difficulties in neurodegenerative disease studies, let's analyze each of the given options: a. True, as we defined above that allelic heterogeneity is the presence of different mutations in a single gene that can cause the same disease. b. True, locus heterogeneity refers to different genes being responsible for causing the same disease. c. True, since allelic and locus heterogeneity complicate the understanding of gene-disease relationships in neurodegenerative diseases. d. Since all options above (a, b, and c) are true, this option is also true. e. Because options a, b, and c are true, this option is false.

Final step: Choose the correct answer

Based on the explanations, the correct answer is d. all of the above.