Marker and Ideal features of molecular markers
What is a marker ?
Markers or genetic markers are simply landmarks on chromosomes that serve as reference points to the location of other genes of interest when a genetic map is constructed.
The rationale of markers is that an easy to observe trait is tightly inked to a more difficult to observe and desirable trait. Genetic markers can be detected at both the morphological level and molecular level or cellular level and classified as morphological and molecular marker.
The ideal features of molecular markers
Below are the characteristics of an ideal marker
- Marker should be polymorphic
- It should have multiple alleles it further helps in differentiation
- Marker should be codominant in nature it must be able to differentiate between homozygous and heterozygous alleles
- Ideal genetic marker should be free of any developmental stage specificity
- The marker should be non epistatic
- The marker should be evenly distributed throughout the genome
- An ideal marker must be simple, efficient and inexpensive
- The marker should need only small amount of tissue and DNA samples to yield good results
- An ideal marker should provide adequate resolution of the various genetic differences in the different bands
- An ideal marker should generate multiple independent and reliable markers
Classification of Molecular markers
- Non PCR based or Hybridisation based markers
- PCR based techniques
1.Non PCR based
- RFLP Restriction Fragment Length Polymorphism – Southern blot technique is used, it requires more amount of DNA and is quite cumbersome
- AFLP (Amplified Fragment length Polymorphism) -> It partly utilizes both PCR and Southern blot (RFLP+RAPD)
2.PCR based marker
a.Arbitarily primed PCR based techniques -> RAPD, DAF, AP-PCR, AFLP, ISSR
b.Sequence specific DNA markers -> SSR, SNP and SCAR markers
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