So what is genomics, anyway?

My daughter--who's in Public Health now--asked me to define genomics.I told her that genomics was the study of genetic inheritance in populations, with a specific focus on disease conditions thought to have a major genetic component.

"So," says my daughter, "how does that differ from epidemiology? or population genetics?"

I blundered through, as usual, and then looked it up online. Although I started with Wikipedia, I finally chose the definition from the CDC national office of public health genomics as an appropriate one for her question:

 What is Genomics?

Genetics is the study of inheritance, or the way traits are passed down from one generation to another. Genes carry the instructions for making proteins, which direct the activities of cells and functions of the body that influence traits such as hair and eye color. Genomics is a newer term that describes the study of all the genes in a person, as well as the interactions of those genes with each other and a person’s environment.

Oops, that definition doesn't include population--it only defines genes in a single person. And, it doesn't take other organisms into account.

The Wikipedia definition doesn't include populations, either. But, it does refer to other organisms:

Genomics is the study of an organism's entire genome. Investigation of single genes, their functions and roles is something very common in today's medical and biological research, and cannot be said to be genomics but rather the most typical feature of molecular biology.

Genomics can be said to have appeared in the 1980s, and took off in the 1990s with the initiation of genome projects for several biological species. A major branch of genomics is still concerned with sequencing the genomes of various organisms, but the knowledge of full genomes has created the possibility for the field of functional genomics, mainly concerned with patterns of gene expression during various conditions. The most important tools here are microarrays and bioinformatics. Study of the full set of proteins in a cell type or tissue, and the changes during various condition, is called proteomics.

STOP! OVERLOAD! How like scientists to invent more terms than anyone outside science can keep track of.

Wikipedia goes on to tell us

As of January 2005, the complete sequence was known of about 1,000 viruses, 220 bacterial species and roughly 20 eukaryote organisms, of which about half are fungi. [4]

Ironically, Wikipedia doesn't include anything about populations.

I've boiled it down to

Genomics is the study of organisms' entire genomes [note the plural, organisms].

The "human genome" is the agreed-upon sequence of nucleotide bases (DNA) identified in the human genome project. This "standard human genome"--although no one ever calls it that--is based on a selection of individuals and a selection of base sequences in that group of individuals.

Besides sequencing DNA, the study of genomics also attempts to determine how the DNA functions, what changes (mutations) affect those functions, and how one individual organism's DNA differs from the standard genome. Human genomics, then, is involved in the sequencing of entire genomes and in the investigation into DNA function.

But, DNA doesn't function in a vacuum. So, human genomics must also consider all other activities occurring in all cells of an individual human. Other parts of the cell may also affect both function and inheritance. Furthermore, genes are influenced by their environment.

Now, let's consider that one person's DNA generally matters to that one person and those genetically related to that person. Can we make the jump now to public health genomics?

Public health genomics covers a LOT of area--as you might already have figured out. Most often, the phrase refers to the study of human health conditions where genetics plays a major part in determining public health. For example, for years we have thought that "juvenile", or Type 1, diabetes appeared in a human at a relatively young age depending on genes inherited by that human from his/her ancestors.

By comparing the complete genomes (DNA samples) of some people with Type 1 diabetes with DNA samples from people without Type 1 diabetes, scientists in Iceland and other locations have been able to identify a number of genetic differences they believe relate to the condition. These have now been called, "diabetes genes".

Now, we're into public health genomics. Whole genomes have been compared--even though the detailed sequences of each genome were not identified. Differences have been found. Scientists can investigate the mapping locations of the sequences responsible for these differences, can develop tests to identify these "genes", can study the effect of environment on these genes, can develop ways to prevent and/or treat Type 1 diabetes--at the gene level.

This is public health genomics.

Well, much of it--So, what do you think?

Marie Godfrey, PhD

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