Molecular genetics
Molecular genetics is a branch of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms.
It integrates these disciplines to explore things like genetic inheritance, gene regulation and expression, and the molecular mechanism behind various life processes.
The discovery of DNA as the blueprint for life and breakthroughs in molecular genetics research came from the combined works of many scientists.
[6] In the mid 19th century, anatomist Walther Flemming, discovered what we now know as chromosomes and the separation process they undergo through mitosis.
His work along with Theodor Boveri first came up with the Chromosomal Theory of Inheritance, which helped explain some of the patterns Mendel had observed much earlier.
The discovery of DNA as a means to transfer the genetic code of life from one cell to another and between generations was essential for identifying the molecule responsible for heredity.
[10] In 1953 Francis Crick and James Watson, building upon the X-ray crystallography work done by Rosalind Franklin and Maurice Wilkins, were able to derive the 3-D double helix structure of DNA.
One noteworthy study was performed by Sydney Brenner and collaborators using "amber" mutants defective in the gene encoding the major head protein of bacteriophage T4.
[22] Today, through the application of molecular genetic techniques, genomics is being studied in many model organisms and data is being collected in computer databases like NCBI and Ensembl.
The computer analysis and comparison of genes within and between different species is called bioinformatics, and links genetic mutations on an evolutionary scale.
[25] The genetic code is made of four interchangeable parts othe DNA molecules, called "bases": adenine, cytosine, uracil (in RNA; thymine in DNA), and guanine and is redundant, meaning multiple combinations of these base pairs (which are read in triplicate) produce the same amino acid.
[27] An organism's genome is made up by its entire set of DNA and is responsible for its genetic traits, function and development.
Nucleotides are the building blocks of DNA, each composed of a sugar molecule, a phosphate group and one of four nitrogenous bases: adenine, guanine, cytosine, and thymine.
It is these four base sequences that form the genetic code for all biological life and contains the information for all the proteins the organism will be able to synthesize.
Often, a secondary assay in the form of a selection may follow mutagenesis where the desired phenotype is difficult to observe, for example in bacteria or cell cultures.
The cells may be transformed using a gene for antibiotic resistance or a fluorescent reporter so that the mutants with the desired phenotype are selected from the non-mutants.
Model organisms like the nematode worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and the zebrafish Danio rerio have been used successfully to study phenotypes resulting from gene mutations.
[36] Although these techniques have some inherent bias regarding the decision to link a phenotype to a particular function, it is much faster in terms of production than forward genetics because the gene of interest is already known.
This technique allows researchers to pinpoint genes and locations of interest in the human genome that they can then further study to identify that cause of the disease.
This technique can be used to detect congenital genetic disorder such as down syndrome, identify gender in embryos, and diagnose some cancers that are caused by chromosome mutations such as translocations.
For example, certain genetic variations in individuals could make them more receptive to a particular drug while other could have a higher risk of adverse reaction to treatments.
