Lesson Explainer: Genetics and Health Science

In this explainer, we will learn how to describe examples of genetic technologies that have improved human health, including the production of golden rice and the Human Genome Project.

When you say you are related to someone, you usually mean genetically. What about a stranger in your town or someone on the other side of the world? Do you think you share any commonalities with them? It might surprise you to learn that all humans share about of their DNA!

This was discovered through the Human Genome Project.

You will recall that the genetic material, or DNA, is located in the nucleus of an animal cell. DNA is organized into chromosomes. Within the chromosomes, there are genes that contain specific instructions for certain characteristics like eye color or height. This is shown in Figure 1.

Example 1: Recalling the Definition of a Gene

What key term is given to a section of DNA that contains the information needed to produce a certain characteristic (e.g., eye color)?

1. Trait
2. Chromosome
3. Genotype
4. Gene
5. DNA

Answer

DNA is the genetic material of the cell. It is located in the nucleus of a cell and organized on chromosomes. In humans, there are 46 chromosomes, and together this is about 6 billion DNA base pairs.

There are genes throughout this sequence of DNA that contain specific instructions for certain traits. For example, there are specific genes that control eye color or height within our DNA. The genotype is the collection of genes that an organism has that give rise to a certain trait.

You can see how some of these terms are represented in the image below.

Therefore, the key term that is given to a section of DNA that contains the information needed to produce a certain characteristic is gene.

In humans, there are 46 chromosomes that contain about 6 billion DNA base pairs in total. The total genetic material of an organism—the sequence of every DNA base pair from beginning to end—is called the genome. Within the genome are about 20‎ ‎000 genes.

Sequencing the human genome was a massive, international project that took over ten years and $2.7 billion dollars to complete. It was mostly completed in 2003. The goals of this project were to accurately sequence all the base pairs of the human genome and to discover all the genes. This would make it possible to identify and study the genes responsible for certain diseases.

For each gene, the genome actually contains two copies, one that is received from the mother and one from the father. Thus, to study the structure of the genome and identify the location of genes, it is enough to analyze half of the DNA. So instead of analyzing 6 billion base pairs, they only needed to sequence 3 billion base pairs in the Human Genome Project.

Even with only half the DNA, it is still a lot of work to sequence 3 billion base pairs! To give you an idea of how massive of a project this was, here is the first 3‎ ‎000 DNA bases of the human genome:

That is about of the entire human genome! If those 3‎ ‎000 DNA bases occupied a single page in a book, the book would be 1 million pages long!

The human genome contains about 20‎ ‎000 genes.

One of the shortest genes in humans is about 800 DNA base pairs long and is called the SRY gene. This gene causes the development of the testes. Without this tiny gene, there would be no human males!

One of the longest genes is the DMD gene, which makes an important protein in muscle tissue. This gene is 2.4 million DNA base pairs long and represents about of the entire human genome!

By determining the sequence of the human genome, scientists have learned more about how we evolved as a species. One of our closest relatives, the chimpanzee, shares about of its DNA with us. In humans, there is even more similarity, with about of our DNA being the same.

There’s a lot of information in the human genome, and scientists are still trying to figure it out. Humans are genetically very similar to each other, and these small differences can be studied to see why some people are more vulnerable to certain diseases.

The Human Genome Project has given us a tool to learn more about ourselves and to fight disease. By learning more about specific genes, in humans and other organisms, we can use them to our advantage. An example of this is golden rice.

People can have health problems if they do not get enough nutrients in their food. Nutrients include carbohydrates, fats, proteins, minerals, and vitamins. People who do not get enough nutrients are said to be deficient for that nutrient.

In developing countries, vitamin A deficiency is a serious problem. Vitamin A is important for vision, the immune system, and reproduction.

Without enough vitamin A, blindness can occur and sometimes even death. In fact, the World Health Organization estimates that 2.7 million children could be saved from death if they had enough vitamin A from their food.

Vitamin A deficiency is most common in communities that depend on rice as their major food source. Vitamin A is actually made in the body from provitamin A (or carotene), which is in the foods we consume that have yellow to red colors. Unfortunately, rice does not contain provitamin A, so diets that are mostly rice based can lead to vitamin A deficiency.

Genetic technology can be used to make a rice plant that produces a lot of provitamin A, so that when people eat it, they get enough vitamin A in their diet. This is possible by inserting the gene for provitamin A into rice. This gives the rice plant the trait of producing provitamin A, which can be converted to vitamin A after consumption. This process is called genetic modification.

Genetically modifying rice to make provitamin A gives the rice grains a golden color, so it is called golden rice. You can see it in the image below.

There are several steps involved in genetically modifying golden rice. First, the gene for vitamin A production (provitamin A) needs to be extracted. Then, this gene is inserted into the seeds of a normal rice plant. When these seeds are planted and grow, golden rice is produced. This is shown in Figure 4 below.

Different studies in the 2000s and 2010s have shown that golden rice is an effective source of vitamin A. Golden rice also grows normally and tastes just like normal rice. The only difference is the golden color and that it is more nutritious!

Besides golden rice, many crops have been genetically engineered to give other advantages. For example, some corn crops are resistant to insects. Other crops, like tomatoes, can be made to be more firm so they are not easily bruised during shipping.

Genetically modified plants offer a lot of advantages, but this still has some people worried. For example, if farmers are all growing the same corn that is resistant to the same insect, what happens if another insect comes around that can wipe out the crops? Because of the lack of diversity, we could find ourselves in a situation where we are in trouble.

People are also worried about the health effects of consuming genetically modified plants. Because we are eating things that are not normally in plants, this might cause an allergic reaction.

There has been a lot of research into the safety of these crops, and the World Health Organization states that all genetically modified foods currently available have passed safety assessments and no effects on human health have been shown.

Let’s recap some of the key points we have covered in this explainer.