Detail information about marker assisted breeding of livestock

1. Dr. Surbhaiyya Shobha Devidas
Ph.D (Agricultural Biotechnology)

2. Course Title- Animal Biotechnology
(BT-3513)
Marker Assisted Breeding of
Livestock

3.  In developed countries animal breeding is base on quantitative
genetics
Nicolas, 1996
 Quantitative genetics is multifactorial, influenced by both gene
and environmental factors and their interactions
Beuzen et al., 2000
 Improvement of livestock focuses on the selective breeding of
individuals with superior phenotypes
Williams, 2005
 MAS (Marker Assisted Selection) is a powerful tool in animal
breeding, improves the whole range of desirable traits
Introduction

4.  It is a process whereby a marker (morphological,
biochemical or one based on DNA/RNA variation) is used
for indirect selection of a genetic determinant
 Used in plant and animal breeding
 Exploits the genetic linkage between markers and important
crop traits (Edwards et al., 1987; Paterson et al., 1988)

5. Morphological Markers
 Animals are selected based on appearance.
 Disadvantage: lack of polymorphism

6. Biochemical Markers
Animal are selected on the basis of biochemical properties.
Eg. Hb, AMYLASE, BLOOD GROUPS ETC.
Disadvantage:
Age dependent
Influenced by environment
It covers less than 10%of genome

7. Molecular Markers/ Ideal features
 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
 Ideal features of molecular marker
1. Highly polymorphic.
2. Simple inheritance.
3. Abundantly occur throughout the genome.
4. Easy and fast to detect,
5. Minimum pleiotropic effect.

8. 1. Reliability.
Markers should be tightly linked to target loci, preferably less
than 5 cM genetic distance.
2. DNA quantity and quality.
Some marker techniques require large amounts and high
quality of DNA, which may sometimes be difficult to obtain in
practice, and this adds to the cost of the procedures.
There are six main considerations for the use
of DNA markers in MAS:

9. 4. Technical procedure.
Highly simple and quick methods are highly desirable.
5. Level of polymorphism.
Ideally, the marker should be highly polymorphic in
breeding material
6. Cost.
The marker assay must be cost-effective in order for MAS
to be feasible.

10.  Ideally markers should be <5 cM from a gene or QTL
Markers must be tightly-linked to target loci!
• Using a pair of flanking markers can greatly improve
reliability but increases time and cost
Marker A
QTL
5 cM
RELIABILITY FOR
SELECTION
Using marker A only:
1 – rA = ~95%
Marker A
QTL
Marker B
5 cM 5 cM
Using markers A and B:
1 - 2 rArB = ~99.5%

11. Markers must be polymorphic
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
RM84 RM296
P1 P2
P1 P2
Not polymorphic Polymorphic!

12. Details about Markers Assisted
selection
 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.
NO YES

13. CONVENTIONAL BREEDING
P1 P2

14. MARKER-ASSISTED BREEDING
P1 X P2

15. MAXIMIZE
GENETIC
GAIN
TO REDUCE
POPULATION SIZE
FOR TRAITS
LEVEL OF
RECOMBINATI
ON BETWEEN
MARKER AND
QTL
Combined approaches

16. Advantages
1. Analysis of the genes helps in identification of the traits an individual will
pass on to the next generation, regardless of the environmental conditions.
2. Selection based on traits when the phenotype is not easy to evaluate such as
for disease resistance genes.
3. Selection is possible for recessive genes and mutants.
4. Faster selection process because an individual’s phenotype can be predicted
at a very early stage.

17. 1. Time consuming
2. Costly
3. Genotyping the whole population is also difficult
4. Gene pyramiding
Limitations

18. 1. Disease resistance
2. Selection and breeding
3. Fertility and reproductive efficiency
4. Maintenance requirements
5. Milk production and maternal ability
6. Growth performance.
Applications

19. Future challenges

20.  In the future to make MAS effective in large
breeding populations, the availability of large-
scale genotyping methods and infrastructure that
allows the generation of hundreds of thousands of
molecular data at a reasonable cost will be necessary
Future prospectus

21. © 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458