Gene Loci Provide the Address of Genetic Information
- When a mutation causies a disease, how do scientists determine which gene is responsible?
- This is where the concept of a gene's locus becomes critical.
- By pinpointing the exact location of a gene on a chromosome, you can uncover its role and how changes in its sequence might lead to disease.
Definition
Locus
A locus (plural: loci) is a gene’s exact location on a chromosome. It acts as the “address” that enables scientists to find and study genes within the human genome.
- The human genome is organized into 23 pairs of chromosomes, each containing thousands of genes.
- These genes are distributed across 22 autosomesand the two sex chromosomes(X and Y).
Genes on Different Chromosomes Assort Independently
- Genes on separate chromosomes assort independently during meiosis, following Mendel’s second law,
- While genes close together on the same chromosome often exhibit linkage.
Linked genes defy Mendel’s law of independent assortment because their proximity means they are inherited together more often than by chance.
Databases Uncover Gene Loci and Their Functions
- Modern genetic research relies heavily on databases like Ensembl and NCBI, which provide detailed information about gene loci and their functions.
- To explore gene loci, follow these steps:
- Search for a gene (e.g., PAH, associated with PKU).
- Identify its locus (e.g., 12q23.2) and protein product.
- Use genome browsers to visualize nearby genes and study functional relationships.
- Use a database to find the locus of the PAH gene, which is associated with phenylketonuria (PKU).
- What chromosome is it located on, and what is its polypeptide product?
Gene Loci Drive Medical and Scientific Discoveries
- Inheritance Patterns: Linked genes affect how traits are passed on, influencing genetic counseling and predictions.
- Genetic Disorders: Mapping loci helps diagnose and treat conditions like sickle cell anemia or cystic fibrosis.
- Evolutionary Insights: Comparing loci across species reveals evolutionary connections and conserved functions.
Ethical Considerations Surround Gene Mapping
- While gene mapping offers immense potential, it raises challenges:
