INTRODUCTION TO GENE

There are about 25,000 to 35,000 genes inside each cell in the human body. The genes carry information that determines what the organism is like, how it survives, and how it behaves in its environment. The genes carry information that determines an organism trait. The parents pass some of their characteristics to the offspring through genes. For example, if the parents have blue eyes, the child might inherit the trait of blue eyes from them. Genes aren’t just in humans, all animals and plants have genes too.

Most living organisms are made up of cells that contain a substance called deoxyribonucleic acid (DNA). DNA is wrapped together to form structures called chromosomes. The genes hang out in chromosomes. Chromosomes come in pairs, and there are hundreds, sometimes thousands, of genes in one chromosome.

Human have 23 pairs of chromosomes - or a total of 46. Individual sperm and egg cells, however, have just 23 unpaired chromosomes. You received half of your chromosomes from your mother's egg and the other half from your father's sperm cell. A male child receives an X chromosome from his mother and a Y chromosome from his father; females get an X chromosome from each parent. But not every living thing has 46 chromosomes inside of its cells. For instance, a donkey has 31 pairs of chromosomes, a hedgehog has 44, and a fruit fly has just 4.

THE FUNCTION OF GENES

The DNA consists of a long combination of four different nucleotide bases (chemicals). The four chemicals are adenine, thymine, cytosine, and guanine (A, T, C, and G). These chemicals can form many possible combinations. Different combinations of the letter ATCG will give people different characteristics. The DNA patterns are also the codes for manufacturing proteins.

Proteins are the building blocks for everything in your body. Proteins made up bones, teeth, hair, earlobes, muscles and blood. Those proteins help our bodies grow, work properly, and stay healthy. Scientists today estimate that each gene in the body may make as many as 10 different proteins. That's over 300,000 proteins!

Genes also come in pairs like chromosomes. Each living organism has two copies of each of genes, and each parent passes along just one copy to make up the genes an offspring have. Genes that are passed on to offspring determine many of its traits, such as hair color and skin color.

For example, Kelly’s mother has one gene for black hair and one for brown hair, and she passed the brown hair gene on to Kelly. If her father has two genes for brown hair, that could explain her brown hair. Kelly ended up with two genes for brown hair, one from each of her parents.

GENE DISORDER

Gene mutation occurs when the cells contain changes or variants in the information of the gene. It usually happens when the cells are aging or have been exposed to certain chemicals or radiation. Cells would identify the mutation and repair them by themselves. However, gene mutation can cause cancel or other illnesses. If the gene mutation exists in egg or sperm cells, children can inherit the mutated gene from their parents.

Researchers have identified more than 4,000 diseases that are caused by genetic variants. A person will not really get the disease although he has the genetic mutation. Because a person inherit a gene from each parent, if the person get one disease gene and one normal gene, the disease gene usually does not cause any problem as normal gene can allow your body to make the normal protein it needs.

On average, people probably carry from 5 to 10 variant or disease genes in their cells. Harm occurs when there is a dominant gene or same recessive disease gene is present on both chromosomes in a pair. Harm can also occur when the variant genes interact with each other or the environment. This has increase vulnerability to diseases.

A person will usually have the disease if he or she carries the dominant disease gene. There is 50 % chance for his or her children to inherit the gene and get the disease. Achondroplasia (a form of dwarfism), Marfan syndrome (a connective tissue disorder), and Huntington disease (a degenerative disease of the nervous system) are example of disease caused by a dominant gene.

Carriers are people who have one recessive gene for a disease and don’t usually have the disease because they have a normal gene of that pair that can do the job. However, there are 25% chance for the child to get the disease if both the parent are carriers. Cystic fibrosis (a lung disease), sickle cell anemia (a blood disease), and Tay-Sachs disease (which causes nervous system problems) are caused by recessive disease genes from both parents coming together in a child.

Some recessive genetic mutations are carried only on the X chromosome. The guys will usually develop the disease because they have only one X chromosome. On the other hand, girls would need to inherit two copies of the recessive gene to get the disease because girls have two X chromosomes. X-linked disorders include the bleeding disorder hemophilia and color blindness.

Sometimes the new cell gets too many or too few chromosomes when the sperm and egg unite. Most children born with Down syndrome, which is associated with mental retardation, have an extra chromosome number 21.

People can have genetic testing if they worried that they might carry certain variant genes. Pregnant women can also have tests done to see if the fetus they are carrying might have certain genetic illnesses. A sample of someone's blood, skin, or amniotic fluid, and is taken and checked for signs of genetic diseases or disorders in a genetic testing.

GENE THERAPY

Gene therapy uses the technology of genetic engineering to cure or treat a disease caused by a gene that has changed in some way. One method they are trying is inserting healthy genes to replace the sick genes. Viruses are often used to carry the healthy genes into the targeted cells because many viruses can insert their own DNA into targeted cells.This science is still in its early stages. However, there has been some success. Gene therapy also studied by scientists to use to treat cancer. One of the methods 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.

However, Scientists haven't yet identified every gene in the human body or what each one does. A map of the entire human genome (all of the genetic material on a living thing's chromosomes) was recently completed by the Human Genome Project and related projects but it will take many more years to find out what each gene does and how they interact with one another. Scientists don't know if and how genes play a role for most diseases. Besides, there are major difficulties inserting the normal genes into the proper cells without causing problems for the rest of the body.

Ethically troubling reasons, such as changing genes to make smarter or more athletic children are also concern because no one knows what are the long-term effects of that kind of change would be.

Still, gene therapy holds the hope for many people who have generic disease that they or their children will be able to live better, healthier lives.