Markers and mapping: we are all geneticists now

Abstract

SUMMARYThis is a review of genetic mapping with molecular markers aimed at the non-specialist who wishes to use, or at least grasp the concepts behind, this powerful analytical tool. Restriction fragment length polymorphisms (RFLPs) are defined and used to illustrate the different aspects of mapping. The principles of segregation, recombination and linkage are considered and related to the idea of a molecular marker map. A description of a typical mapping population and how it is analysed follows. Traits to be mapped are divided into those controlled by 'major' genes and those governed by quantitative trait loci (QTLs). Exploitation of the map for marker-assisted selection, gene cloning and synteny comparisons is discussed, as are some of the limitations to the usefulness of molecular marker maps. Finally other marker systems are introduced, namely minisatellites or variable number tandem repeats (VNTRs); randomly amplified polymorphic DNA (RAPDs); microsatellites or simple sequence repeats (SSRs); and amplified fragment length polymorphisms (AFLPs).

The Genetic Basis of Smoltification-Related Traits in Oncorhynchus mykiss

“…In other words, resident and anadromous O. mykiss in sympatry exhibit some level of gene flow, and there is evidence for plasticity in the expression of the alternative life histories. The close genetic relationship between resident and anadromous life-history types in sympatry is not unique to O. mykiss, but is found in other salmonid species that exhibit variation in anadromy vs. residency (Hindar et al 1991;Jones et al 1997;Quinn 2005). With possible multiple parallel examples of life-history diversification within and across salmonid species, the question remains whether the same or different sets of genes play a role in the diversification of (1) anadromous and resident salmonid life histories and (2) timing of migration in anadromous species.…”

Recent Advances in QTL Mapping and Quantitative Disease Resistance Approach

“…Apart from the use of DNA markers in the construction of linkage maps, they have numerous applications in plant breeding such as assessing the level of genetic diversity within germplasm and cultivar identity (Baird et al, 1997;Henry, 1997;Jahufer et al, 2003;Weising et al, 1995;Winter and Kahl, 1995). DNA markers may be broadly divided into three classes based on the method of their detection: (1) hybridization-based; (2) polymerase chain reaction (PCR)-based and (3) DNA sequencebased Jones et al, 1997;Joshi et al, 1999;Winter and Kahl, 1995). Essentially, DNA markers may reveal genetic differences that can be visualised by using a technique called gel electrophoresis and staining with chemicals (ethidium bromide or silver) or detection with radioactive or colourimetric probes.…”

“…Biochemical markers, which include allelic variants of enzymes called isozymes; and DNA (or molecular) markers, which reveal sites of variation in DNA (Jones et al, 1997;Winter and Kahl, 1995).…”

Breeding rootstocks for Prunus species: Advances in genetic and genomics of peach and cherry as a model

“…There are three main types of markers: (i) morphological, also called classical or visible, which are phenotypic traits, (ii) biochemical, which are mostly isoenzymes, and (iii) molecular (or DNA), which are DNA sequences that have single-nucleotide polymorphisms (SNPs) or insertion/ deletion (INDEL) polymorphisms that can be detected or identified by various techniques based on polymerase chain reaction (PCR), sequencing, or hybridization (Winter and Kahl, 1995;Jones et al, 1997;. Molecular markers are the most widely used, mainly because they are abundant and not affected by environmental factors or the developmental or physiological state of the plant (Winter and Kahl, 1995).…”