MOLECULAR MARKERS

What is Marker? Marker is a piece of DNA molecule that is associated with a certain trait of a organism Morphological Types of Markers Genetic Biochemical Chromosomal

Animals are selected based on appearance Morphological Markers Animals are selected based on appearance Eg. PIGMENTATION Disadvantage: lack of polymorphism

Biochemical Markers Animals are selected based on biochemical properties Eg. Hb, AMYLASE, BLOOD GROUPS ETC. Disadvantage: Sex limited Age dependent Influenced by environment It covers less than 10% of genome

Animals are selected based on structural & numerical variations Chromosomal Markers Animals are selected based on structural & numerical variations Eg. Structural and Numerical Variations Structural- Deletions, Insertions etc. Numerical- Trisomy, Monosomy, Nullysomy Disadvantage: low polymorphism

Molecular Marker Revealing variation at a DNA level Characteristics: Co-dominant expression Nondestructive assay Complete penetrance Early onset of phenotypic expression High polymorphism Random distribution throughout the genome Assay can be automated

Methodological Advantages DNA isolated from any tissue eg. Blood, hair etc. DNA isolated at any stage even during foetal life DNA has longer shelf-life readily exchangeable b/w labs Analysis of DNA carried out at early age/ even at the embryonic Stage irrespective of sex.

Molecular Markers Single locus marker Multi-locus marker Microsatellite Single locus marker RFLP STS Molecular Markers DNA Fingerprinting RAPD Multi-locus marker AFLP

Applications of markers in cereal breeding Assessing variability of genetic differences and characteristics within a species. Identification and fingerprinting of genotypes. Estimating distances between species and offspring. Identification of DNA sequence from useful candidate genes

It has 5 applications in fisheries and aquaculture: Species Identification Genetic variation and population structure study in natural populations Comparison between wild and hatchery populations Assessment of demographic bottleneck in natural population

A genetic marker is a gene or DNA sequence with a known location on a chromosome and associated with a particular gene or trait. It can be described as a variation, which may arise due to mutation or alteration in the genomic loci that can be bserved. A genetic marker may be a short DNA sequence, such as a sequence surrounding a single base-pair change (single nucleotide polymorphism, SNP), or a long one, like mini & micro satellites

Recent years have witnessed a great interest towards molecular markers, revealing polymorphism at the DNA level, as they play an important role in animal genetics studies. Sometimes the term “Smart Breeding” is used to describe marker supported breeding strategies

The main aim of the breeder is to select animal with superior genetic potential as parents for the next generation. The first attempt to improve animals used the phenotype of an animal for a specific trait as a tool for selection. This application uses external animal characteristics as a marker that called morphological markers (i.e. udder shape, coat color, body shape, skin structure, and anatomical characteristics)

These markers depend on visual observation and measurement to identify, classify, and characterize the genetic evolution of different species or populations. The conclusions reached through applying morphological markers are often not completely accurate when they used for the evaluation of farm animal genetics, because these markers based on subjective judgments and descriptions. Another type of markers represents by using of cytological markers that were included several criteria such as chromosome karyotypes, bandings, repeats, translocations, deletions, and inversions .