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 99.9% 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.

Definition: Gene

A gene is a sequence of DNA that contains the information needed to produce a certain characteristic (e.g., eye color).

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. Within these 6 billion base pair sequences are about 20‎ ‎000 genes. The total genetic material of an organism—the sequence of every DNA base pair from beginning to end—is called the genome.

Definition: Genome

The genome is all the genetic material of an organism.

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.

Key Term: Human Genome Project

The human genome project was a massive project to sequence the genome of humans.

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:

Figure2

That is about 0.0001% 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 0.08% 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 99% of its DNA with us. In humans, there is even more similarity, with about 99.9% of our DNA being the same.

Example 2: Recalling How Similar the Human Genome Is between Humans

The Human Genome Project found that the genomes of humans are very similar. Roughly, what percent of the human genome is shared between humans?

  1. 80%
  2. 88%
  3. >99%
  4. 75%
  5. 50%

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. Genes are sequences of DNA that contain instructions for certain inheritable traits, such as eye color.

The complete set of DNA in an organism is called its genome.

The Human Genome Project was a massive project that aimed to sequence the human genome. Upon its completion, which took over 10 years, we discovered that we had about 3 billion base pairs of DNA and 20‎ ‎000 genes.

When the genome of one human is compared to another, about 99.9% of it is the same.

Therefore, >99% is shared between humans.

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.

Key Term: Deficiency

Deficiency is the lack of a certain nutrient, which can cause health problems.

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

Key Term: Vitamin A

Vitamin A is an important nutrient needed for normal vision and a healthy immune and reproductive system.

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.

Key Term: Genetic Modification

Genetic modification is a technique used to change the traits of an organism by inserting a gene with that trait into the organism.

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.

Golden image

Figure3

Key Term: Golden Rice

Golden rice is genetically modified rice that contains high levels of provitamin A.

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.

Example 3: Recalling the Steps to Genetically Modify Golden Rice

The following are the three stages of producing golden rice, in the wrong order:

X. Insert the gene for provitamin A production into the seeds of a rice plant.

Y. Find and extract the gene that controls provitamin A production.

Z. Grow these seeds to produce full plants.

Place them into the correct order.

Answer

Without enough vitamin A in the diet, blindness and death can occur. This is a big problem in developing countries that consume a lot of rice, as rice does not contain vitamin A.

It is possible to genetically modify rice to contain the gene for provitamin A production. This can be used to enrich rice to help people get enough vitamin A in their diet.

You will recall that DNA is the genetic material of the cell. It is located in the nucleus of a cell and organized on chromosomes. Genes are sequences of DNA that contain instructions for certain inheritable traits such as eye color in humans or the color of the grains in rice.

With genetic modification, the gene for vitamin A production can be inserted into a normal rice plant to make “golden rice” that can make high levels of provitamin A.

There are several steps to genetically modifying the rice plant to make golden rice.

First, the gene for provitamin A production needs to be discovered and extracted. Then, this gene is inserted into the seeds of a rice plant. Then, these can be planted and grown to produce full plants that produce the genetically modified rice plant.

Therefore, the correct sequence for producing golden rice is Y, X, and Z.

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.

Key Points

  • The Human Genome Project aimed to sequence all 3 billion base pairs of the human genome.
  • By knowing the DNA sequence of the human genome, it is possible to identify genes involved in certain diseases to hopefully treat those diseases.
  • In developing countries, vitamin A deficiency is a serious problem that can lead to blindness.
  • By inserting the gene for provitamin A into rice, scientists can produce golden rice to combat vitamin A deficiency.

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