Genetic and Physical Map Correlation

Abstract

Abstract Genetic and physical maps illustrate the arrangement of genes and DNA markers on a chromosome. The relative distances between positions on a genetic map are calculated using recombination frequencies, whereas a physical map is based on the actual number of nucleotide pairs between loci. These maps are a key resource for understanding genome organisation. They are the basis for map‐based cloning and marker‐assisted selection, serving as a bridge between breeding and sequencing research. A comparison of marker position and order may provide interesting insight into the evolutionary history of even distantly related species. Physical and genetic maps can unravel the complexities of large duplicated genomes intractable to sequencing efforts; whereas in species more amenable to genetic studies high‐resolution maps provide the scaffold on which whole genome sequences are assembled. A complete genome sequence is a physical map at its highest resolution. Key Concepts: Genetic maps are based on the recombination frequency between molecular markers. These maps are population specific. Physical maps are an alignment of DNA sequences, with distance between markers measured in base pairs. Unique DNA sequences called molecular markers are compared to each other to determine correct marker order (genetic map) and used to identify overlapping segments of larger DNA pieces (physical map). Genetic mapping is based on recombination, the exchange of DNA sequence between sister chromatids during meiosis. High‐resolution genetic and physical maps serve as the scaffold for genome sequence assembly. Tightly correlated marker order between species can identify conserved syntenic regions.