Chromosome mapping determines gene locations on chromosomes, aiding understanding of physical traits and disease treatment. Genetic linkage shows inherited genes are passed on in groups. Gene and physical mapping distinguish gene order and location. Methods include breeding experiments and microbiological techniques.
Chromosome mapping is the process of determining the locations of specific genes on a chromosome. Chromosomes are collections of deoxyribonucleic acid, or DNA, that contain genes, although exactly where within the chromosomes these genes are located is not well understood. Creating a chromosome map is useful for understanding how genes give rise to physical traits in living things. Mapping of chromosomes can also be important in treating disease by allowing doctors to identify the genes that cause disease. There are several types of chromosome maps, each with varying levels of accuracy and completeness.
Every living organism contains a set of operating instructions within long molecules called DNA. These molecules are found within every cell of the body and are grouped into chromosomes. Specific units of these molecules, called genes, have been found to be responsible for physical traits in the body, such as eye color or blood type. Understanding genes, therefore, allows scientists to understand physical traits in living things.
Some genes on a chromosome tend to be inherited together with adjacent genes. This trend, called genetic linkage, was discovered in the early 20th century. During human reproduction, a baby’s chromosomes are formed from a complicated combination of the parents’ chromosomes. It is known that the genes of each parent’s chromosomes can be passed on in groups. Discovering the locations of genes on chromosomes, therefore, could make it easier to understand how genes are inherited and expressed in offspring.
It is important to distinguish between two different procedures related to chromosome mapping. Gene mapping, or sequencing, consists of obtaining an ordered list of genes on a strand of DNA. This is similar to making a numbered list of every exit along a highway. Physical mapping, on the other hand, determines the physical location of genes on a particular chromosome. It’s more like identifying landmarks in the area near each exit on a highway.
There are several methods used in chromosome mapping. Historically, relative gene positions have been inferred from breeding experiments with organisms. This has been done extensively with the fruit fly species Drosophila melanogaster. While certain traits were often inherited together, it was assumed that the responsible genes were located close to each other. This method is useful in mapping chromosomes to determine the relative, rather than absolute, location of genes.
Physical maps can be made using modern microbiological techniques. DNA strands are sometimes separated and broken into fragments for further study. These maps can vary greatly in resolution. Resolution in physical genetic mapping is the degree of separation that can be detected in closely related genetic elements.
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