What is a Gene? What are Genes?

Every living organism has genes. Genes are a set of instructions that decide what the organism is like, how it survives, and how it behaves in its environment.

The genes lie in long strands of DNA (deoxyribonucleic acid) called chromosomes. Humans have 23 pairs of chromosomes - or a total of 46. A donkey has 31 pairs of chromosomes, a hedgehog has 44, and a fruit fly has just 4.

A gene consists of a long combination of four different nucleotide bases (chemicals). There are many possible combinations. The four nucleotides are:

A (adenine)

C (cytosine)

G (guanine)

T (thymine)

Different combinations of the letters ACGT give people different characteristics. For example, a person with the following combination - AAACCGGTTTTT - may have green eyes, while somebody whose combination is - AAACCGGTTTAA - may have blue eyes. If fact, the last two letters - TT - and - AA - mean the color, and the first ten letters - AAACCGGTTT - mean the eye. (this gene formula is a simplification; in reality they would be much longer).

So, to recap in slightly more detail:

• Genes carry the codes ACGT. We have thousands of genes. They are like our computer program and make each one of us what we are. A gene is a tiny section of a long DNA double helix molecule, which consists of a linear sequence of base pairs. A gene is any section along the DNA that has instructions encoded that allow a cell to produce a specific product - usually, a protein, such as an enzyme - that triggers one precise action. There are between 50,000 and 100,000 genes, and every single gene is made up of thousands, even hundreds of thousands, of chemical bases.


• Chromosomes comes from the Greek Chroma, which means color, and Soma, which means body (chromosomes are stained very strongly by some dyes). Chromosomes are the long strands of DNA. They are organized structures of DNA and protein and are found in cells. Humans have 23 pairs of chromosomes. An enormous number of genes lie in each chromosome strand. Scientists say that a chromosome is a single piece of DNA which has many genes, regulatory elements and other nucleotide sequences (sequences of the letters ACGT).
  
  
A chromosome consists of DNA and has proteins attached to it. These chromosomes are located in your body's cells, which then contain this important genetic information held in the long strands of DNA.


• DNA (deoxyribonucleic acid) is the chemical that appears in strands (see picture - below right). Every cell in your body has the same DNA. Each person's DNA is different - this is what makes each of us unique. DNA is made up of two long-paired strands spiraled into the famous double helix. Each strand contains millions of chemical building blocks called bases.

Your genes make you what you are

a DNA strand - gene is a short section of this strand

Your genes decide virtually everything about you. Here is a list of some of the basic features and characteristics than your genes are programmed to do.

Your genes decide..

• whether you are tall or not
• the color of your hair
• the color of your skin
• whether you are more likely to develop certain diseases
• whether you are good at sports
• how you respond to environmental triggers
• what you look like inside and out

Our genes are our inheritance

We get our genes from our parents. Scientists say that a gene is a basic unit of heredity in a living organism. Anything that lives depends on genes. They possess the data to build and maintain cells and pass genetic information to offspring.
Each of your cells contains two sets of chromosomes - one set came from your mother while the other came from your father - male sperm and the female egg carry a single set of 23 chromosomes each - 22 autosomes and an X or Y sex chromosome. If you are female you inherited an X chromosome from each parent - if you are male you inherited an X chromosome from your mother and a Y from your father.

The Human Genome Project (HGP)

The Human Genome Project was a global project aimed at determining the sequence of the chemical pairs that make up human DNA. The HGP had another goal - to identify and map the 20,000-25,000 or so genes that make up the Human Genome.
The undertaking started in 1990, headed by James Watson who worked at the NIH (National Institutes of Health), along with other scientists from the USA, Canada, New Zealand and Great Britain. The researchers came up with a working draft in 2000. Three years later, in 2003, the Human Genome Project was just about completed. Further analysis is still being published today.
Scientists say that mapping the human genome brings us much closer to developing effective treatments for hundreds of diseases.
Not only did the HGP focus on humans, it also looked at other organisms and animals, such as the fruit fly and E. coli.
The HGP is the largest single research ever carried out in modern science. Over three billion nucleotide combinations have been found in the human genome (combinations of ACGT). The project had aimed to sequence 95% of human DNA, so far 99.99% has been sequenced.

What is Gene Therapy?

Genes are inserted into a patient's cells and tissues to treat a disease, usually a hereditary disease. This science is still in its early stages. However, there has been some success.
Scientists are currently studying various ways of treating cancer using gene therapy. One is to try to enhance a healthy cell's ability to fight cancer. Another is to target the cancer cells themselves - to destroy them or prevent their growth.

Gene testing a person's susceptibility to cancer

BRCA1 is a gene which significantly raises a woman's chances of developing breast cancer. Today, it is possible for woman to have a test to find out whether she carries that gene. BRCA1 carriers have a 50% chance of passing the anomaly to each of their children.

Genetic tests to find your ideal treatment

Scientists say that one day we will be able to test a patient to find out which specific medicines are best for him or her, depending on that person's genetic makeup. Some medicines work well for some patients, but not for others.

News on Genetics

The Medical News Today website includes an individual category on genetics news, allowing you to keep up-to-date with the latest research via website, RSS, weekly newsletter and daily news alerts.

Sources - The Genome Project, NIH, Wikipedia.