Genetics

Understanding genetics

Genetics is the study of genes and how they impact over several generations in a variety of organisms. As such, it is a branch of biology. It was discovered in the 1800s that certain inherited traits affected species of pea plants. This accounted for what we now call genetic variation in evolution. When genetics was first being thought about, however, the term unit of inheritance tended to be used. We now know that molecular mechanisms are at play in all living things that impact on what future generations will look like and behave. These molecules are called genes and the study of them – and their effects – is, therefore, called genetics.

When we inherit a trait - for example, hair colour – from a parent, it is not the gene, strictly speaking, that is inherited. Instead, it is what is called an allele. This is a gene variation. The genetic pioneer, Gregor Mendel, theorised about alleles by observing the colours of flowers. He supposed that male plants could offer one of two alleles and the same occurred with females. Depending on the colour of the flower of both parents, so the colour of the flower of the offspring plant could be determined. Humans have the same diploid form of genetic inheritance that relies on these pairs of alleles.

Genetics and deoxyribonucleic acid, better known as DNA, are not exactly the same, but they are linked. In DNA, there are four types of encoded molecular information. These are called nucleotides. In the long chains of spiralling DNA that exist in all living things – including people, of course – these nucleotides can be arranged in many different ways. Depending on the sequence of these arrangements, different genetic codes can be written into them. As such, you can think of genes as individual letters but DNA as words, sentences and even paragraphs of information. Though one would not exist without the other, they cannot be described as the same thing.

In Mendel's early experiments with pea flowers, he found that one allele was dominant over the other. This accounted for why more purple plants flowered than white ones. You only need one allele of a dominant trait to inherit it. However, for a recessive gene to be apparent, then you need both alleles to be the same, from your mother's as well as your father's genetic code. In people, the presence of freckles is a dominant trait. The way you clasp your hands together and whether your ear lobes are attached to your head or not are also down to similar genetic traits.

Genes are much better understood these days, and genetic studies are going on into all sorts of medical conditions, some of which were previously thought to have no genetic link. Some inherited conditions are known to be caused by genetics, such as Down's Syndrome, for example. Vitamin D absorption is also known to have a genetic link as is colour blindness. People who suffer from acne also probably have the gene that promotes it, too.