A new crop of crops
How can a plant be part firefly?
Here’s a riddle for you to solve. What has green leaves and glows like a firefly? Did you guess a firefly plant? Well, firefly plants don’t exist. Or do they? In a famous experiment shown here, scientists made a kind of “hybrid” using a firefly and a plant. A new technology makes it possible to cross two very different kinds of living things. What is this new technology? Before you learn about it, you need to learn about genes.
Working With Genes
Take another look at the firefly. It’s easy to see that this organism has a set of characteristics, or traits-six legs, hard outer wings, yellow stripes, saw-shaped antennae. The organ that produces a firefly’s glow is another trait. Each kind of organism has its own traits.
The cells of organisms contain information that control straits.For example , a fire fly’s cells contain the information about the organ that makes a firefly glow. A wheat plant’s cells contain information about the color and shape of wheat flowers. Where is this information? The nucleus of each cell contains threadlike strands called chromosomes. Each and every chromosomes are divided into sections called genes. A gene is a unit of information that controls a trait.
Each kind of living thing has a set of genes that controls its traits. Genes that control a firefly’s traits are different from genes that control a plant’s traits.
And the genes of different organisms do not mix. Why? In nature fireflies mate with fireflies, cats mate with cats, wheat plants pollinate wheat plants. You won’t find a firefly plant in nature. So how did scientists make one in a laboratory?
As scientists learned about genes, they wondered whether a gene from one organism could be put into another organism. Genetic engineering is a way to change the traits of an organism by changing its genes. Using genetic engineering, scientists removed a gene from a firefly and added it to a plant. The plant glowed like a firefly!
Scientists are using genetic engineering to produce new varieties of crop plants. These new plants can help farmers in the same ways hybrids do. For example, scientists might be able to give crop plants new genes that would protect the plants from insect pests. Then farmers wouldn’t have to use as many pesticides on their crops.
Genetic Engineering
How does genetic engineering work? Scientists use several different methods. One way is to use a carrier-an organism that carries the gene from one organism to another. This method is shown in the diagram. Touch each step as you follow the procedure of transferring a gene from one kind of plant to another kind of plant.
First, scientists choose two plants. One of the plants has a desirable trait, such as resistance to a particular disease. The second plant does not have this desirable trait. Next, scientists take a cell from the plant with the desirable trait, and remove the gene that controls the trait. How do they do it? Scientists use a special chemical to cut the gene out of the chromosome.
Then the gene is put inside a carrier organism-a bacterium. Remember, bacteria are simple, one celled organisms. Many kinds of bacteria have a ring like structure called a plasmid. Scientists remove the plasmid from the bacterium and cut it so that it has two “sticky” ends. Then scientists “glue” the plant gene to the sticky ends of the plasmid. Finally, the plasmid is put back into the bacterium. Now the bacterium is ready to carry the new gene to the second plant.
In the last steps, scientists take a cell from the plant that doesn’t have the trait. They put this cell into contact with the bacterium. The bacterium infects the plant cell with a disease. During the infection, the new gene becomes part of the chromosome in the plant cell.
But one more step remains. The plant cell-with its new gene-must grow into a new plant, with roots, stems, and leaves. Scientists place the cell in a liquid that contains nutrients and plant hormones. The plant cell grows and develops into a young plant. All the cells in the new plant have the gene that controls the new trait. So, the genetically engineered plant has resistance to disease!
Designer Foods
How might plants with new genes help farmers, like those in this picture, grow food? Well, think about what plants need to grow. Remember that plants need nutrients. Ask farmers to name the secret to growing large crops, and they’ll say, “NitrogenBut chemical fertilizers are getting more expensive. Also, they can be harmful to the environment .When rain falls , fertilizers wash from the soil into rivers and lakes. The nutrients in fertilizers cause water pollution. To solve these problems, scientists are trying to develop new kinds of plants that don’t need to be fertilized. Instead, the plants would make their own natural fertilizers nitrogen compounds. Remember that legumes make nitrogen compounds, with the help of Rhizobium bacteria. Now scientists are planning different ways to get other crop plants-corn, wheat, and rice-to make nitrogen compounds, too.
One kind of experiment is shown in the diagram.
You might call it the “fix it yourself” experiment. Why? It’s working with the group of genes that control Rhizobium’s ability to “fix” nitrogen, or change nitrogen gas into nitrogen compounds. Using the methods you just learned about, scientists plan to remove the genes from Rhizobium bacteria.
Next, the scientists would try to put the genes into cells of corn, wheat, or rice plants. The scientists hope that the genetically engineered plants would be able to do what Rhizobium does-make nitrogen compounds. If these genetic engineering experiments work, just think about what it would mean. All the corn fields and wheat fields in the world might not need to be fertilized for nitrogen!
