What is genetic linkage?
Q: What is genetic linkage?
A: Genetic linkage occurs when alleles at different loci do not segregate randomly, breaking Mendel's second law. Genes are linked when they are on the same chromosome and tend to stay together during meiosis.
Q: How can alleles on the same chromosome be separated?
A: Alleles on the same chromosome can be separated by crossing over of DNA during meiosis, when the chromosomes segregate. The probability of this happening increases if the alleles are far apart on the chromosome, as it is more likely that a cross-over will occur between them.
Q: What technique was used for mapping genes on chromosomes?
A: The first technique used for mapping genes on chromosomes was to calculate relative distance between two genes using offspring of an organism showing two linked genetic traits. The percentage of offspring where the two traits do not run together is noted, and higher percentages indicate closer locations of genes on a chromosome.
Q: What is a genetic map unit (m.u.) or centimorgan?
A: A genetic map unit (m.u.), or centimorgan, is defined as the distance between genes for which one product of meiosis in 100 is recombinant. A recombinant frequency (RF) of 1% is equivalent to 1 m.u..
Q: How does one create a linkage map?
A: A linkage map can be created by finding the map distances between a number of traits that are present on the same chromosome, ideally avoiding significant gaps between traits to avoid multiple crossovers occurring simultaneously.
Q: What happens if there are significant gaps between traits in creating a linkage map?
A: If there are significant gaps between traits in creating a linkage map, it increases the possibility that multiple crossovers will occur simultaneously which could lead to inaccurate results being obtained from mapping gene locations and distances from each other along chromosomes
