In 1865 a monk named Gregor Mendel in Austria proposed that hereditary traits passed from parents to offspring were the result of unseen “factors” that contained the information from generation to generation. Mendel came to the conclusion by crossbreeding pea plants. His curiosity stemmed from the observations he made of the pea plant’s flower colors. When he crossed plants with white and purple flowers the offspring all had purple flowers. Why purple but not white or a mix like pink? For his initial work with the pea plants, which was substantial for the time and holds true in many cases for modern genetics, Gregor Mendel is credited as the founder of genetics.
After Mendel’s proposal it was later discovered that the “factors” were located in the nuclei of cells, in bands called chromosomes. Specific traits, such as blue eyes or purple flowers, as in Mendel’s garden peas, are located in short stretches on the chromosomes. One chromosome will contain many genes and together these hold all of the developmental information of every living organism. Genetics is the study of genes and chromosomes, their translation and inheritance. Although that definition appears simple it has proven very complex and highly useful. Genetics has become an invaluable tool for fighting various diseases; it is used in courtrooms to defend or condemn suspects, and it has also made its way into archeology and zoology.
How Do Genes Work?
Genes are made of four different nucleotide bases. A nucleotide is a molecule composed of a nitrogen base, a phosphate group, and a sugar. The four bases are adenine, thymine, guanine, and cytosine. Adenine (A) is always paired with thymine (T). Cytosine (C) is paired with guanine (G). Strung out together these bases form two strands in a double helix like a twisted ladder.
On a chromosome genes are wound tightly, like thread over a spool. When a cell prepares to divide it unwinds the genes from their positions on the chromosome and splits the strands apart. Because adenine always bonds with thymine and guanine with cytosine the cell can remake the gene strands, copying them exactly. If one strand reads AATTCGCG then the enzymes in the cell will create a complementary strand to read TTAAGCGC.
Cells draw on genetic information to produce proteins. To do this the cell unwinds the DNA and transcribes it into mRNA, messenger RNA, which is processed by the cell as instructions for making protein.
Genes, Diseases, and the Future
As scientists uncover more about genes, and learn to manipulate them, many diseases have been linked to genes. For some conditions, like Huntington’s, if a person is found to have the genes for the disease they will contract it if they don’t already have it. However, in the case of cancer, the presence of a gene marking a susceptibility does not guarantee the illness will follow.
As the science of genetics progresses, exciting new opportunities continue to appear. Genetics could provide the cure to the elusive HIV virus. Genetically modified plants and animals could help feed the starving around the world. Yet, like any other new technology, genetics has inspired its fair share of controversy. Should bacterial genes be spliced into plants to create “natural” pesticides? Is it safe for humans to eat? Other ethical concerns rise up when one considers that in the not-too-distant future parents may be able to genetically engineer their children. Even the possibility of curing HIV involves experimental gene manipulation.
Scientists have only scratched the surface of the genome. While there is reason for great excitement, it must be restricted by caution and responsibility.
 |
