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Molecular markers

Molecular Markers and there Applications

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Molecular markers

  1. 1. What are Molecular Markers? Specific fragments of DNA that can be identified within the whole genome. Molecular markers are the general assays that allow detection of the sequence differences between two or more individual. Molecular markers are found at specific locations of the genome.  They are used to 'flag' the position of a particular gene or the inheritance of a particular characteristic or desired characteristics Definition A molecular marker is a DNA sequence that is readily detected and whose inheritance can easily be monitored .
  2. 2. Marker systems are tools which is used to mark a trait in living organism MORPHOLOGICAL MARKER: Classical markers MOLECULAR MARKERS: Variation in macro-molecules BIOCHEMICAL MARKERS GENETIC MARKERS ISOENZYME PROTEIN RFLP AFLP RAPD They are protein produced by expression of gene Depend upon sequence of DNA •Low polymorphism •Requires expression of trait / gene •Dominance effect •Expression sex limited •Expressed late in life
  3. 3. DNA markers Non-PCR Based,  RFLP- Restriction fragment length polymorphism. PCR Based RAPD- Random amplification of polymorphic DNA. AFLP-Amplified fragment length polymorphism.  SCAR-Sequence characterize amplified region. STS- Sequence tagged sites. EST-Express sequence tags. SNP-Single nucleotide polymorphism. SSR-Simple sequence repeats CAPS-Cleaved amplified polymorphic sequences.
  4. 4.  it must be polymorphic.  Co-dominant inheritance.  A marker should be evenly and frequently distributed throughout the genome.  It should be easy, fast and cheap to detect.  It should be reproducible.  High exchange of data between laboratories. Properties of Ideal Genetic Marker
  5. 5. Feature RFLP RAPD AFLP SSR or Microsatellite DNA required (µg) 10 0.02 0.5-1.0 0.05 DNA quality High High Moderate Moderate PCR-based No Yes Yes Yes No. of polymorphic loci analysed 1.0-3.0 1.5-50 20-100 1.0-3.0 Ease of use Not easy Easy Easy Easy Reproductibily High Unreliable High High Development cost Low Low Moderate High Cost per analysis High Low Moderate Low Table 1 : Comparision of the most broadly used techniques of molecular markers Cont…..
  6. 6. Definition The variation(s) in the length of DNA fragments produced by a specific restriction endonuclease from genomic DNA s of two or more individuals of a species RFLP
  7. 7. Principle Restriction fragment length polymorphism (RFLP) technology was first developed in the 1980s for use in human genetic applications and was later applied to plants. By digesting total DNA with specific restriction enzymes, an unlimited number of RFLPs can be generated. RFLPs are relatively small in size and are co-dominant in nature. If two individuals differ by as little as a single nucleotide in the restriction site, the restriction enzyme will cut the DNA of one but not the other. Restriction fragments of different lengths are thus generated. All RFLP markers are analyzed using a common technique. However, the analysis requires a relatively complex technique that is time consuming and expensive.
  8. 8. The hybridization results can be visualized by 1. Autoradiography (if the probes are radioactively labeled), or 2. Chemiluminesence (if non-radioactive, enzyme-link methods are used for probe labeling and detection). Any of the visualization techniques will give the same results. The visualization techniques used will depend on the laboratory condition Principle
  9. 9. Principle
  10. 10. -simple method as no sequence specific information is required -codomonant markers -it is not depend on PCR -it required large amount of highly pure DNA -it require constant supply of probes -it is laborious to identify suitable markers -it is time consuming -it requires expertise in autoradiography Advantages Disadvantages
  12. 12. Any DNA segment that is amplified using short oligodeoxynucleotide primer of arbitrary nucleotide sequence (amplifier) and polymerase chain reaction procedure (Khal, 2001) RAPD also known as, AP-PCR(Arbitrarily primed PCR), DAF (DNA amplification fingerprinting)& MAAP(Multiple arbitrary amplicon profiling) RAPD are a dominant marker system Definition RAPD
  13. 13. 1. RAPDs are produce by PCR using genomic DNA and arbitrary primers 2. Taq polymerase is used to amplify DNA segment between closely spaced sequence (< 2kb) and complementary to the short random oligomers (typically 10-mers) 3. RAPD polymorphism result from change in the primer-binding site in the DNA sequence Principle
  14. 14. In variety A there are 4 primer binding sites resulting in two RAPD products, variety B lacks one of the binding sites resulting in only one RAPD marker being produced
  15. 15. Template DNA Primers point in the same direction, so amplification won’t happen
  16. 16. Template DNA Primers too far apart, so amplification won’t happen > 2,000 bases
  17. 17. Template DNA Primers are just the right distance apart, so fragment is amplified 100 - 1,500 bases
  18. 18. Protocol 1) Master Stock Mixture 2) Add 25µl of master mix to 5µl of your DNA in a sterile tube Note: In each PCR run you conduct, include 2 sample, one of control DNA without primer (3µl DNA), and one sample without DNA (5µl ddH2O)
  19. 19. -need small amount of DNA -it involves non-radioactive assay -it does not required specific probe libraries -it provide quick and efficient screening for DNA sequence based on polymorphism at many loci -it is inherited as dominant traits -there is a bands due to relatively short primer -the production of non-parental bands in the offspring of known pedigree warrants its use with extreme care -it is sensitive to change in PCR conditions Advantages Disadvantages
  20. 20. APPLICATION of RAPDApplication of RAPD
  21. 21. AFLP Definition Any difference between corresponding DNA fragment from two organisms A & B that is detected by amplified restriction length polymorphism technique
  22. 22. Principle 1. The amplified fragment length polymorphism technique combines components of RFLP analysis with PCR technology. 2. Total genomic DNA is digested with a pair of restriction enzymes normally a frequent and rare cutter. 3. Adaptors of known sequence are then ligation to the DNA fragments. 4. Primer complementary to the adaptors are used to amplify the restriction fragments. 5. The PCR amplified fragments can then separated by gel electrophoresis and banding patterns visualized. 6. A range of enzymes and primer are available to manipulate the complexity of AFLP fingerprint to suit application
  23. 23. Principle Genomic DNA For restriction digestion we use two type of cutter i.e •Rare cutter (6bp) EcoRI •Frequent cutter (4bp) MseI Interstitial cohesive ends Adaptor ligation PCR amplification using EcoRI/MseI
  24. 24. -extremely sensitive -it has a wide scale applicability -it discriminates heterozygotes from homozygotes when a gel scanner is used -used for mapping -it is highly expensive -it required more DNA than RAPD -it required experience of sequencing gels Advantages Disadvantages
  25. 25. Application of AFLP
  26. 26. (Microsatellite) SSR
  27. 27. Microsatellites can be amplified for identification by the polymerase chain reaction (PCR) process, using the unique sequences of flanking regions as primers DNA is repeatedly denatured at a high temperature to separate the double strand, then cooled to allow annealing of primers and the extension of nucleotide sequences through the microsatellite. This process results in production of enough DNA to be visible on agarose or polyacrylamide gels. With the abundance of PCR technology, primers that flank microsatellite loci are simple and quick to use, but the development of correctly functioning primers is often a tedious and costly process. Principle
  28. 28. -simple and easy to use -easy to detect via PCR -co-dominant marker -perfectly suited for used in map-based cloning -cost is higher for establishing polymorphic primer sites and investment in the synthesizing the oligonucleotides -initial identification, DNA sequence information necessary Advantages Disadvantages
  29. 29. Application of SSR  Assessment of genetic variability and characterization of germplasm.  Identification and fingerprinting of genotypes.  Estimation of genetic distances between population, inbreeds and breeding material.  Marker assisted selection.  Identification of sequence of useful candidate genes
  30. 30. F1 identification An autoradiograph detecting parent (P1&P2) and homozygous and heterozygous (H ) F1 segregation Applications:- 1
  31. 31. No. Plants Allele MG3H1_146 MG3H_150 MH3H1_169 Resistance 1 Ge004 3-001 MG3H001_146 1 - - Resistence ym4 2 -002 MG3H001_169 - - 1 Susceptible 3 -003 MG3H001_146 1 - - Resistence ym4 4 -004 MG3H001_169 - - 1 Susceptible 5 -005 MG3H001_146 1 - - Resistence ym4 6 -006 MG3H001_146 1 - - Resistence ym4 7 -007 MG3H001_169 - - 1 Susceptible 8 -008 MG3H001_169 - - 1 Susceptible 9 -009 MG3H001_150 - 1 - Resistence ym5 10 -010 MG3H001_150 - 1 - Resistence ym5 11 -011 MG3H001_150 - 1 - Resistence ym5 12 -012 MG3H001_169 - - 1 Susceptible Table : Application of PCR-based marker MG3H001 for detecting resistant allele169 bp corresponds to the susceptible plant(s), alleles 146 bp and 150 bp to the ym4 or ym5 resistant plants, respectively. Germany Korzun, 2002
  32. 32. M R H H S R H H S R H H S H R R H R H Fig: Identification of RAPD marker link to brown plant hoper resistance gene in rice June et al.,2003 3
  33. 33. RAPD-ANALYSIS OF GENETIC VARIATION OF FOUR IMPORTANT RICE VARIETIES USING RAPD PRIMERS Amplified RAPD patterns of OPR1 M - 1 Kb DNA Ladder 1 - ADT38 2 - ASD16 3 - IR20 4 - PONNI Amplified RAPD patterns of OPR2. Mani et al. (2010)Tamil Nadu Con.. 2
  34. 34. UPGMA dandogram based on Nei’s (1978) original measure of genetic distance, summarizing the data on differentiation between four samples of O. sativa genotypes according to RAPD analysis. Genetic distance between O. sativa populations of four different rice varieties based on Nei’s 1978 measures of genetic distance. PONNI IR-20 ADT38 ASD16 PONNI 0.3913 1.7776 1.02564 IR-20 0.3913 1.60944 1.95601 ADT38 1.77767 1.60944 0.8574 ASD16 1.02564 1.95601 0.8574
  35. 35. 1 2 3 4 5 Fig: Molecular mapping of fertility restorer gene in basmati rice using micro satellite marker. Delhi Mishra et al.2001 A Rice microsatellite marker RM 258 identified to be linked with fertility restorer gene in PRR- 78 using bulk segregant analysis. DNA marker (lane 1). Restorer line PRR 78 (lane 2). CMS line IR 58025 (lane 3). Fertile bulk showing heterozygous pattern (lane 4). Sterile bulk showing homozygous pattern (lane 5)
  36. 36. Fig. 7 : Hybrids identification by using seed protein markers Bhubaneshwar Panigrahi et al., 2001
  37. 37. Advantage Disadvantage
  38. 38. Advantage Disadvantage
  39. 39. Advantage Disadvantage
  40. 40. Advantage Disadvantage
  41. 41. Advantages:  Highly variable  Easy to detect via PCR  Fast evolving  Co dominant Disadvantage:  Relatively expensive and time consuming to develop  Initial identification, DNA sequence information necessary
  42. 42. 46 PCR: Polymerase Chain Reaction  “Amplify” DNA by in-vitro (in plastico) synthesis  Key requirements:  enzyme: Taq DNA polymerase, not denatured at high temps used to denature DNA  primers: short (~ 20 b) oligonucleotides bind to denatured DNA, required to start DNA synthesis
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