Pardon, for leaving this blog for a quite a while, I am busy preparing my master degree in Edinburgh which will be commenced this September. I will study Quantitative Genomics which require me to have a strong mathematical thinking. This essay is a summary of one preparatory reading for the courses. *Finger crossed
Human have been developing agriculture and faming since centuries ago and proven to be enough to feed all of people. The astronomical population increase these decades, partly due to improvement in health care, demands human to supply food resources far higher and it will keep rising every year. To keep up with this fact, the superior agricultural species which have high yield are absolutely required.
Conventionally, the selection of species with advantegious trait is done by using phenotype selection. In this method, breeders pick individual with desired trait and put aside the others. The selected is then subjected to several cycles of crossing which end up in species with desired trait in homozygous state. However, some crucial traits are difficult to asses or only be specifically expressed in one sex (such as milk production in cattle which can only be measured in reproductively mature female). This will impede the progress of creating species with high productivity.
The advance in genetics and plumetting price of whole genomic sequencing are potentially can resolve the issue. The real breeding value of species is determined by analyzing their whole genomic profile. This breeding value then be used for designing the breeding scheme to obtain the species with desired trait.
Target loci of desired trait is often obscure and hard to detect in precise, so breeder use indirect marker instead. The markers are specific DNA sequence spread across genome and have been mapped. The markers is could be repetitive DNA (such as mini or microsatelite) or single base difference loci (SNP / Single Nucleotide Polymorphism). This selected markers should be in disequilibrium with the target loci, so that both DNA will be inherited together. The presence of specific marker also indicates the existense of desired loci, so the selection become easier. Nevertheless, across generation the power of selection will be reduced as the association of marker with target gene will break down as the result of genetic recombination during meiosis. Therefore, the good marker is the one which located closer with the target gene.
Utiliizing genetic marker will accelerate selection process which result in more genetic gain obtained. Genetic gain is an indicator of the trait improvement towards the desired trait and positively correlated with intensity of selection, the extent of genetic variation and selection intensity. Molecular selection plays a part in speeding up the selection interval which inverse with genetic gain, so genetic gain will be obtained quickly compared to phenotypic based selection. So, it can be concluded that the usage of molecular genetics will enhance the selection process compared with traditional breeding selection and potentially be exploited to keep up with the demand of food resources.