Final answer:
A candidate locus is a suspected but unproven region of the genome that may influence a quantitative trait, while a quantitative trait locus is a known region affecting such a trait. QTL mapping identifies these loci through statistical analysis, and marker loci are genetic locations associated with specific traits.
Step-by-step explanation:
The locus suspected but not proven to contribute to variation in a certain quantitative trait is known as a candidate locus. This term describes a region on a chromosome which is hypothesized to contain a gene or genes that influence a specific quantitative trait. A quantitative trait locus (QTL), on the other hand, is a specific section of the genome that has been identified as affecting a quantitative trait such as height or weight. QTL mapping is the process by which scientists identify the precise locations of QTLs on the genome, and it generally involves statistical correlations between genetic markers (like SNPs, or single nucleotide polymorphisms) and variation in the quantitative trait.
In genetics, marker locus and qualitative traits, or discrete traits, are defined differently; a marker locus is a specific location on a chromosome known for being associated with a particular trait, while qualitative traits are characteristics that can be categorized and are typically controlled by a single gene locus with different alleles producing distinct phenotypes, like Mendelian traits. Quantitative traits involve multiple genes (polygenic), and their expression is often influenced by environmental factors and are typically measured on a continuous scale.