An Introduction to Genomics

The Difference between Genetics and Genomics

Isn’t genomics just the same thing as genetics? After all, they both have to do with DNA, right?

Not exactly. Both of these topics do study DNA and genes, but at entirely different levels. Genetics is the study of genes, genetic information, heredity, and genetic variation. Genomics, on the other hand, is the study of the entire genome of an organism—all of its genes and tissues, at the level of its DNA, RNA, or protein expression.

Genomic Research

Studying the entire genome of an organism—even a bacteria or virus—is an enormous undertaking. Basic genomic research involves determining how many genes an organism has, the functions of those genes, and how expression or suppression of the organism’s genes is influenced by environmental and other factors.

Genomic research also includes a more general field of study known as intragenomic phenomena—interactions between various alleles and loci within the genome. This includes such genomic phenomena as epistasis, heterosis, and plieotropy.

Epistasis occurs when the action of one gene affects the expression of other genes. For example, a gene may code for a protein which, when expressed, prevents the expression of one or more other genes. Epistasis can also occur at the phenotypic level: for example, if an individual has the genetic mutation that causes albinism, the phenotypic effects of genes that control their skin, hair, and eye color will be masked by the lack of pigment caused by albinism.

Heterosis is also known as hybrid vigor, and describes the way in which hybrids of two genetically different parents have increased strength in certain characteristics. This concept is most often applied to the practice of breeding plants and livestock for characteristics such as improved yield or pest resistance.

Plieotropy occurs when one gene influences several phenotypic traits at once. Typically, this phenomenon occurs because the gene codes for a protein which is used by many different types of cells, or is involved in a specific cell-signaling pathway. Mutations in plieotropic genes often have wide-ranging effects. An example is the genetic disorder called phenylketonuria, which can reduce skin and hair pigmentation and cause mental retardation due to a mutation in a gene that converts phenylalanine into tyrosine.

The Potential of Genomic Research

In terms of human health and medicine, the potential of genomic research is simply enormous. Genomic research could potentially…

• Improve the process of drug discovery and design with improved knowledge of drug targets and of how gene expression influences the metabolism of drugs.

• Allow medical professionals to design drug regimens that are specifically tailored to individuals according to their genetic make-up. This approach could mean treatment that is more effective with fewer risks.

  Advertisement

• Allow for earlier, easier, and more accurate diagnosis of genetic disorders. For example, breast cancer has a very strong genetic link. Around 12% of women carry a gene variant that predisposes them to develop breast cancer, and 50% of all cases of breast cancer develop in this 12% of the population.