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A genetic linkage map helps scientists map the order of traits in DNA by showing how often they recombine. It can help find genes that cause genetic diseases. Genetic recombination occurs during meiosis, allowing offspring to have different traits from their parents. DNA markers with higher recombination frequency are shown as distant on the map. Genetic linkage maps are often used as a framework for physical maps to quickly identify particular genes.
A genetic linkage map is a tool used in genetic research to help scientists map the order of particular traits as they appear in a strand of deoxyribonucleic acid (DNA). It does not map the distance between tracts on the DNA strand. Instead, it maps how often they recombine. A genetic linkage map can help geneticists find the genes that cause genetic diseases.
Normally, each cell of a human, plant or animal carries two copies of each gene. Sex cells, such as eggs, sperm, and spores, undergo a process called meiosis or cell division, which splits the cell in half. This leaves only one strand of DNA in each cell.
Genetic recombination occurs before the cell divides. First, the chromosomes form two lines down the center of the cell, making pairs of genes. Sometimes chromosomes break in half. The broken pieces are then combined to make new molecules. This process, known as genetic crossover, happens to each human chromosome an average of 1.5 times for every sex cell that is formed.
This exchange of genetic material is what allows offspring to have different traits from their parents. That’s why two brown-haired parents can produce a blond child. The process of genetic recombination allows a species to genetically adapt to its environment over time. It can also lead to genetic diseases.
Geneticists can use a genetic linkage map to find where certain traits appear. These traits are called DNA markers. Any hereditary trait can be a DNA marker as long as it differs from person to person and can be easily detected in a laboratory. Mapping known traits, such as hair and eye color, can help scientists extrapolate where other traits might appear.
The physical distance between traits on a genetic linkage map is determined by the recombination frequency. DNA markers with higher recombination frequency are shown as distant. Markers with a lower frequency are close together.
It works because genes that are close together are less likely to be separated by recombination. For example, if the gene for blue eyes is next to the gene for blond hair on the genetic linkage map, it is likely that blue-eyed children also have blond hair. If, however, there are many other genes between blue eyes and blonde hair, genetic crossover confusion can separate these traits, resulting in blue eyes and brown hair.
These are just guesses, though. Genetic linkage maps are often used as a framework for physical maps, which are detailed maps of the DNA sequence. They allow scientists to quickly identify particular genes.
