You might already have a general understanding about heredity that – it is carried from parents to their children and will affect the health and physical characteristics of children. But do you want to know more about what is heredity and how it affects the health and other physical and mental characteristics? Then we answer in detail to your questions.
We know that genes play an important role in determining our physical characteristics. But to know how genes work, let’s get into some biology facts. Cells in human body contain a substance called deoxyribonucleic acid (DNA). DNA is wrapped together to form structures called chromosomes.
What is Heredity?
Most cells in human body have 23 pairs of chromosomes, thus making a total of 46. But, individual sperm and egg cells have only 23 unpaired chromosomes. A child receives half of chromosomes from mother’s egg and the other half from 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.
Genes are sections or segments of DNA that are carried on chromosomes and determine specific human characteristics, such as health conditions, hair color, etc. Some characteristics come from a single gene, whereas others come from gene combinations.
Heredity is the passing of genes from one generation to the next. It is what that determines what you are today. Heredity plays an important role, but your environment also influences your abilities and interests.
DNA contains four chemicals – Adeninine, Guanine, Thymine, Cytosine – that are strung in patterns on extremely thin, coiled strands in the cell. The DNA patterns are the codes for manufacturing proteins – chemicals that enable the body to work and grow. Genes hold the instructions for making protein products. As your cells duplicate, they pass this genetic information to the new cells. Genes can be dominant or recessive. Dominant genes show their effect even if there is only one copy of that gene in the pair. For a person to have a recessive disease or characteristic, the person must have the gene on both chromosomes of the pair.
Cells can sometimes contain variants in the information in their genes. This is called gene mutation. It often occurs when cells are aging or have been exposed to certain chemicals or radiation. Fortunately, cells usually recognize these mutations and repair them by themselves. Sometimes, however, they can cause ill health such as some types of cancer. If the gene mutation exists in egg or sperm cells, children can inherit the mutated gene from their parents.
Heredity and Health
There are more than 4,000 diseases that are caused by genetic variants. But, having a genetic mutation that may cause disease doesn’t mean that a person will definitely get that disease. Because you inherit a gene from each parent, having one disease gene may not cause any problems. Normal gene can allow your body to make the normal protein.
People probably carry from 5 to 10 variant or disease genes in their cells. Problems actually arise when the disease gene is dominant or when the same recessive disease gene is present on both chromosomes of a pair. Problems also occur when several variant genes interact with each other – or with environment – that increase susceptibility to diseases.
If a person carries the dominant gene for a disease, he or she will usually have the disease, and each of the person’s children will have a 50% chance of inheriting the gene and getting the disease. Diseases caused by a dominant gene include achondroplasia. Marfan syndrome and Huntington disease.
People who have one recessive gene for a disease are called carriers. They don’t usually have the disease because they have a normal gene of that pair that can do the job. When two carriers have a child together, however, the child has a 25% chance of getting the disease gene from both parents and in turn getting the disease. Cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are caused by such recessive disease genes.
Some recessive genetic variants are carried only on the X chromosome, which means that usually only guys can develop the disease because they have only one X chromosome. Girls have two X chromosomes, so they would need to inherit two copies of the recessive genes to get the disease. X-linked disorders include the bleeding disorder, hemophilia and color blindness.
Sometimes when an egg and sperm unite, the new cell may get too many or too few chromosomes. Most children born with Down syndrome, which is associated with mental retardation, have an extra chromosome number 21. In some cases, people who are concerned that they might carry certain variant genes can undergo genetic testing, so they can learn their children’s risk of having a disease. Pregnant women can also have tests done to see if the fetus they are carrying have certain genetic illnesses or not. Genetic testing usually involves taking a sample of someone’s blood, skin or amniotic fluid, and checking it for signs of genetic diseases or disorders.
Gene Therapy offers Solutions
Gene therapy is a promising new field of medical research. In gene therapy, researchers try to supply copies of healthy genes to cells with variant or missing genes so that the healthy genes will take over. Viruses are often used to carry the healthy genes into the targeted cells because many viruses can insert their own DNA into targeted cells.
But there are many problems with gene therapy. Scientists haven’t yet identified every gene in the human body and what each one can do. Huge scientific efforts like ‘The Human Genome Project’ and related projects have recently completed a map of the entire human genome. But it will take many more years to find out what each gene does and possible interactions between them. For most diseases, scientists don’t know if and how genes play a role. And, there are major difficulties inserting the normal genes into the proper cells without causing problems for the rest of the body.
There are also concerns that people might try changing genes for ethically troubling purposes. No one knows what the long-term effects of that kind of change would be. Still, for many people who have genetic diseases, gene therapy holds the hope. Let us wish that with the advances in gene therapy, present and future generations would be able to live better and healthier lives.
Therefore, heredity does affect our physical as well as mental health. Some of the hereditary diseases are:
- Heart diseases
- Down syndrome
- Cystic fibrosis
- Sickle-cell anemia
- Inflammatory Bowel Syndrome
- Huntington’s disease
Besides the heredity factor, the environmental factor also plays an important role in these diseases. With proper precautions, one might avoid some of the diseases which are passed on because of genes. Basic preventions and lifestyle changes can help one avoid certain hereditary diseases and help us live quality life. Look at the positive aspect, you don’t have to spend a huge amount of money on health care.