Marker assissted selection

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MAS is a powerful tool in animal breeding, improves the whole range of desirable traits

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Marker assissted selection

  1. 1. MOLECULAR MARKERS AND MARKER ASSISTED SELECTION SHAKIL BHAT P.G. SCHOLAR ANIMAL BIOTECHNOLOGY
  2. 2. Introduction  In developed countries animal breeding is based on quantitative genetics Nicolas,(1996)  Quantitative genetics is multifactorial, influenced both by gene and environmental factors and their interaction (Beuzen et al., 2000)  Improvement of livestock focuses on the selective breeding of individuals with superior phenotypes Williams,(2005) MAS is a powerful tool in animal breeding, improves the whole range of desirable traits
  3. 3. MORPHOLOGICAL GENETIC MARKERS BIOCHEMICAL CHROMOSOMAL
  4. 4. MORPHOLOGICAL MARKERS
  5. 5. BIOCHEMICAL MARKERS
  6. 6. CHROMOSOMAL MARKERS
  7. 7. Molecular markers  Molecular marker are specific fragments of DNA that can be identified within the whole genome  They are used to 'flag' the position of a particular gene  Molecular markers are used in molecular biology to identify a particular sequence of DNA (Chauhan and Rajiv, 2010)
  8. 8. Features of Molecular Markers Characteristics: Co-dominant expression Early onset of phenotypic expression High polymorphism Random distribution throughout the genome Assay can be automated
  9. 9. Classes of Molecular Markers  Hybridization- based DNA markers RFLP, oligonucleotide fingerprinting  PCR based DNA markers RAPD, AFLP, SSR  Sequencing based DNA markers and DNA Chip SNP Vogel et al.,(1998)
  10. 10. Restriction Fragment Length Polymorphism (RFLP) Principles  RFLP analysis is a standard, well-tested procedure for estimation of genetic diversity Tanksley, (1993)  RFLP analysis is based on the ability of restriction enzymes to cleave DNA at specific target nucleotide sequences Fairbanks, (1995)
  11. 11. • Simple sequence repeats are present in the genomes of all eukaryotes and consists of several to over a hundred repeats of a 1-4 nucleotide motif.
  12. 12. SNP • The most common genetic polymorphism • Distribute throughout genome with high density • More stable and easy to assay • Facilitates large scale genetic association studies as genetic markers.
  13. 13. MARKER ASSISTED SELECTION
  14. 14. THEORY AND PRACTICE ADVANTAGES MAS vs PHENOTYPIC SELECTION
  15. 15. The process of using the results of DNA-marker testing to predict the genetic merit of the animal being tested and assist in the selection of individuals to become parents in the next generation.
  16. 16. • Marker assisted selection (MAS) is an indirect selection process where a trait of interest is selected not based on the outward appearance of the trait itself but on a genetic marker near the trait (gene) on the DNA.
  17. 17. • MAS - Use of information from genetic markers to help make selection decisions of animals for genetic Improvement. • This is done in a manner that exploits both known major genes and all unknown genes.
  18. 18. CONVENTIONAL BREEDING P1 P2
  19. 19. MARKER-ASSISTED BREEDING P1 X P2
  20. 20. Combined approaches MAXIMIZE GENETIC GAIN LEVEL OF RECOMBINATION BETWEEN MARKER AND QTL TO REDUCE POPULATION SIZE FOR TRAITS
  21. 21. ADVANTAGES TIME COST RECESSIVE GENES LOW HERTIBILITY SEASONAL CONSIDERATIONS GEOGRAPHICAL CONSIDERATIONS GENE STACKING EARLY DETECTION MULTIPLE GENES
  22. 22. REQUIREMENTS QTL DETECTION GENE MAPPING MARKER GENOTYPING GENETIC EVALUATION
  23. 23. Potential benefits from MAS are greatest for traits that Have low heritability Are difficult or expensive to measure (disease resistance) Are currently not selected for as they are not routinely measured (tenderness)
  24. 24. •Time consuming •Difficult MAS Vs. PS •Costly •Performed off season •Gene pyramiding •Early stages of development •Several selections simultaneously •Low heritability traits
  25. 25. MAS in selection programming BETWEEN BREED SELECTION WITHIN BREED SELECTION INTROGRESSION IMPROVEMENT OF SYNTHETIC LINES
  26. 26. CURRENT STATUS OF MAS OBSTACLES CHALLENGES
  27. 27. Low impact of MAS Resources not available Markers may not be cost-effective QTL mapping QTL effects may depend on genetic background or be influenced by environmental conditions Poor integration of molecular genetic and conventional breeding
  28. 28. Cost - a major obstacle
  29. 29. Future challenges

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