Summary: Jaenisch & Bird (2003)

Phenotype is a result of the genotype, but we always seem to focus on the observable differences between organisms rather than digging deeper to understand how they all come to be. Epigenetics plays a major role in gene expression and in turn causes differences in organisms' phenotypes. The nucleotide sequence of DNA remains the same, but the way the gene acts is modified (Epigenetics Group- Garvin Institute of Medical Research, 2010). These modifications affect the expression of the gene, either silencing it or turning it on (Epigenetics Group- Garvin Institute of Medical Research, 2010). We can see the differences in gene activity by the varying characteristics or behaviours that correlate with each gene modification. Sometimes epigenetics occurs by chance while other times it is a response to the environmental setting (Jaenisch & Bird, 2003). This ability to adapt to environmental stimuli demonstrates that epigenetics is a dynamic process. Gene modifications aren't permanent and may change depending on different situations and factors (Jaenisch & Bird, 2003). The regulation of one gene can have multiple implications, as many genes normally interact to accomplish a task. The change in expression of one gene can either inhibit or allow another gene to activate which leads to differences in the phenotype. Once the activity of a certain gene is altered, this new arrangement can be passed down to the offspring of that organism (Jaenisch & Bird, 2003). As a result, new phenotypes may evolve and lead to new populations of species as time passes. One form of epigenetics that is believed to silences the expression of targeted genes is called DNA methylation (Jaenisch & Bird, 2003). Jaenisch and Bird (2003) observed an example of DNA modification in plants that grow in high altitudes. Sometimes these plants experience the urge to flower earlier because of the cold temperatures with which they live in (Jaenisch & Bird, 2003). The Flowering Locus C (FLC) gene is thought to be the gene which reacts to the cold environment, causing flowering to occur prematurely (Jaenisch & Bird, 2003). The combination of DNA methylation and expression of an inhibitory gene (VRN2) silences the FLC gene so that the plant won't flower at the wrong time (Jaenisch & Bird, 2003). In this circumstance epigenetics was able to take environmental factors into account and alter gene expression in a way that the organism was able to better survive. This is only a brief example of the influence of epigenetics on genes. It has many other applications in different species which are currently still being researched.