Gene mapping refers to the process of locating genes within a genome. The regions of a genome that directly encode proteins, or the protein-coding genes, are usually of great interest to scientists. Therefore, it is often a priority to locate each gene in a genome.
Nowadays, a mapping procedure typically involves genome sequencing and analysis of the resulting sequence using digital methods that would let us spot desired genes. Therefore, most gene mapping projects begin with genome sequencing.
Table of Contents
- Gene Mapping Definition
- Types of Gene Mapping
- Genetic Mapping Techniques
- Frequently Asked Questions (FAQs)
Gene Mapping Definition
Gene mapping refers to the techniques used to identify a gene’s location and distance between genes. The distances between various sites inside a gene can also be described through gene mapping.
Placing several molecular markers at specific locations on the genome is the fundamental element of all genome mapping. There are many types of molecular markers. When creating genome maps, genes can be observed as a particular class of genetic markers mapped similarly to other markers.
Types of Gene Mapping
Genetic-linkage maps and physical maps are the two main categories of “Maps” used in gene mapping.
Both maps consist of genetic markers and gene loci. While physical maps involve actual physical distances, often measured in number of base pairs, distances of genetic maps are based on genetic linkage information.
There are many gene mapping methods, including comparative, physical, and genetic-linkage mapping. However, physical, and genetic-linkage mapping are more common.
Genetic-linkage Mapping
Genetic-linkage maps show the location of each gene on a chromosome and their relative distances from one another. Initially, these maps were created by tracing the inheritance of several features, like eye colour and hair colour.
Blood, saliva, or tissue samples from both affected and unaffected family members are used to begin a genetic map. Saliva is the most often used sample in genetic mapping, particularly personal genetic studies.
Genetic mapping is made possible by crossing over — a regular biological occurrence during meiosis (cell division that produces sperm and egg cells). Chromosomes line up in pairs in the centre of a cell during the first phase of meiosis, where they often “stick” to one another and exchange similar fragments of themselves, also known as crossing over.
Genetic mapping makes it possible to determine which gene is present on each chromosome and where it is located within that specific chromosome. Based on the distance between two genes, mapping can also determine which gene is more likely to undergo recombination.
Physical Mapping
Physical maps always provide the actual DNA base pair distances between landmarks. It is one gene mapping approach that has a high degree of accuracy in determining the sequence of DNA base pairs.
A physical map provides the nucleotide numbers and the precise physical distance between genetic markers. Radiation hybrid mapping, sequence mapping, and cytogenetic mapping are the techniques used to produce a physical map.
Physical mapping assembles larger DNA sections using DNA markers and DNA fragments. Researchers can identify the locations of the DNA bases from the overlapping sections of the fragments.
Various physical mapping methods are available to study genomes of multiple sizes and obtain different degrees of precision. Physical mapping is a common approach used in genome sequencing to acquire an entire genome sequence and determine whether there is any correlation between the specific DNA sequence and phenotypic features.
Genetic Mapping Techniques
Recombination events are used in genetic mapping techniques to measure the distance between genetic markers.
- Random Fragment Length Polymorphism, or RFLP, measures the differences in homologous DNA sequences to calculate the distance between two markers.
- Currently, gene mapping analyses targeting single gene disorders use short tandem repeat polymorphisms (STRP).
- SNP (Single Nucleotide Polymorphism) is used in genome-wide association and linkage analysis genetic research. Linkage analysis is studied using the inheritance of characteristic and genetic signatures like SNPs and microsatellites.
- Genome-Wide Association (GWA) studies the connections between traits and markers like SNPs and microsatellites by treating the population as a single family. The method is used to map the gene functions of common disorders.
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