Biotechnology
Think Like a Scientist
This activity explores whether fingerprints are unique.
Step 1: Cover the tip of your index finger completely with ink.
Step 2: Press your finger firmly onto a sheet of paper to transfer your fingerprint pattern.
Step 3: Observe the lines and patterns in your fingerprint. Compare it with fingerprints from your classmates. Are they the same or different?
Step 4: Now compare the fingerprints of identical twins (if available). Are their fingerprints identical?
Step 5: Think about how fingerprints are used in society. Can you name any examples?
Show Answer
Each person has unique fingerprint patterns. Even among classmates, no two fingerprints are exactly the same.
Show Answer
No, even identical twins do not have the same fingerprints. Fingerprint patterns are influenced by genetic and environmental factors during development.
Show Answer
Fingerprints are used in biometric identification for unlocking devices, verifying identity, and in forensic science to solve crimes.
Free vs Attached Earlobes
Look at Figure. Which of the two earlobe types does your ear match?
The shape of the earlobe — whether free or attached — is determined by a specific factor in your body. The presence or absence of a free earlobe is a genetic trait.
You saw in Table 1 that some traits are inherited. This is because the traits come from your parents, and the factors that determine them are passed from generation to generation. In your opinion, what is this factor and where in the body is it found?
Quick Fact
The trait for free or attached earlobes is controlled by a single gene. Free earlobes are a dominant trait, while attached earlobes are recessive.
A Closer Look at the Cell Nucleus
You know that a cell is the basic unit that makes up the body of all living organisms. One part of a cell is the nucleus. Scientists, through many experiments, have discovered that the nucleus contains the instructions for an organism's traits.
But what material is inside the nucleus? You may recall from science that proteins, carbohydrates, and lipids are made by the cell. Another material found in the nucleus is called DNA.
DNA is located in the nucleus and is made up of complex instructions. These instructions contain information for building proteins and for determining traits in all living things.
The segments of DNA that carry specific traits are called genes. Genes are responsible for inherited traits, like eye color or hair shape, that are passed from one generation to the next.
Important Concept: DNA and Genetic Traits
DNA, or Deoxyribonucleic Acid, is a material found inside the nucleus of cells. It contains the complete set of instructions for building and operating the body of an organism.
Segments of DNA are called genes. Each gene carries the information needed to determine a specific trait, such as eye color, hair texture, or height. These traits are passed from parents to offspring through inheritance.
DNA is what makes each individual unique, even though all humans share much of the same genetic code. It is the reason family members often look alike, and why children inherit traits from both parents.
Did You Know?
Based on current scientific data, DNA is shaped like a twisted ladder, called a double helix. Each cell contains nearly 2 meters of DNA!
If you lined up all 250,000 strands of DNA in a single cell, they would fit into a space as thin as a single strand of hair.
Chromosomes Inside the Cell Nucleus
Inside the nucleus, DNA is organized into thread-like structures called chromosomes. Each species has a fixed number of chromosomes in its cells. For example, human body cells contain 46 chromosomes.
Chromosomes can be seen under a microscope, especially when cells are actively dividing.
Common Mistake: Chromosome Count Confusion
It's a common mistake to think that all living organisms have the same number of chromosomes. In fact, each species has a specific chromosome count. For example, humans have 46 chromosomes in each body cell.
Another misunderstanding is assuming that chromosomes are only visible under a microscope at all times. In reality, chromosomes are best observed when the cell is dividing, during which they condense and become clearly visible.
Questions
The table below shows the number of chromosomes in several organisms. Use the data to answer the questions that follow.
| Organism | Number of Chromosomes |
|---|---|
| Human | 46 |
| Chicken | 78 |
| Butterfly | 380 |
| Rice | 24 |
“The number of chromosomes depends on the organism’s complexity.”
Show Answer
The statement is incorrect. The number of chromosomes does not directly relate to how complex an organism is. For example, butterflies have more chromosomes (380) than humans (46).
Show Answer
While the number of chromosomes is part of an organism’s genetics, it cannot be used alone to judge similarity. For instance, chickens and humans have different chromosome counts, yet both are animals with complex systems.
Think Like a Scientist
Is DNA the only factor that determines traits? Try this experiment to find out.
Materials: 1 potato with at least 4 sprouts (eyes), 4 disposable cups, potting soil, water, paper, marker.
Step 1: Fill four cups with moist potting soil. Label them 1 to 4.
Step 2: Cut the potato into 4 pieces so that each piece contains one sprout. Place one piece into each cup.
Step 3: Water each cup according to the instructions below:
| Cup Number | Instructions |
|---|---|
| Cup 1 | Place in a sunny spot and water regularly. |
| Cup 2 | Place in a dark area and water regularly. |
| Cup 3 | Place in a sunny spot but do not water. |
| Cup 4 | Place in a dark area and do not water. |
Observe the cups over the next two weeks. Record which ones sprout and grow best.
Show Answer
The potato in Cup 1 usually grows best because it has both light and water.
Show Answer
No, the environment (light and water) affected how well each piece grew, even though the DNA was identical.
Show Answer
Both DNA and the environment affect traits. While the DNA was the same, only the pieces with the right environment grew well.
How Environment Affects Traits
Some differences between individuals of the same species are caused by environmental factors — these are factors outside the organism's DNA. Figures show some examples of how the environment can affect inherited traits.
These two flowers have different colors because they are growing in different soil types.
These two mice are genetically identical, but their diets are different. Only the mouse in group 1 received food that turned on a specific gene.
In these rabbits, cold temperature affects fur color. When part of the body is cooled, the fur in that area grows darker.
Many traits are not determined by DNA alone. While inherited traits come from parents, the environment also plays a critical role. For example, a person’s health depends on both their genes and their lifestyle choices like diet and exercise.
Can you think of any other traits in humans or animals that may be influenced by both DNA and environmental factors?
Quick Fact
Not all traits are determined solely by DNA. Environmental factors such as temperature, nutrition, and sunlight can influence how genes are expressed — or even whether they are activated at all.
For example, identical twins may look slightly different as they grow older because of differences in their lifestyles and environments.
Creating New Traits in Organisms
Scientists have gained a deep understanding of genes and how they function. This knowledge has allowed them to modify genes in order to give organisms new traits.
For example, people with diabetes often lack the ability to naturally produce insulin. Insulin is a hormone that regulates blood sugar. Scientists have used gene technology to insert the human insulin gene into bacteria. These bacteria can now produce insulin, which can then be harvested and used as a medicine.
Genetic engineering is also used in agriculture. Scientists have inserted a gene responsible for making vitamin A into rice plants. The result is a type of genetically modified rice known as Golden Rice, which has a yellow tint. This rice helps prevent vitamin A deficiency, especially in populations that rely heavily on rice as their staple food.
Did You Know?
In many poor countries, people's diets consist mainly of cooked grains. This has led to widespread vitamin A deficiency. Each year, hundreds of thousands of children are at risk of blindness due to this deficiency.
Golden Rice contains a substance that the body converts into vitamin A. However, this genetically modified rice is not yet widely produced in those countries.
Think Like a Scientist
Fish gene in a tomato?!
A few years ago, researchers created a type of tomato that contained a gene from a fish. The gene helped the fish survive in freezing temperatures. When inserted into the tomato's DNA, it gave the tomato plant similar resistance to cold.
Look at the DNA strands below. The left strand contains the resistance gene from the fish. The center shows tomato DNA with no added genes. On the right, the fish gene has been added to the tomato DNA.
2. The gene is inserted into tomato DNA to produce a frost-resistant tomato.
Show Answer
Genes carry instructions for making proteins. When the fish gene is inserted into the tomato DNA, the tomato plant starts making the same protein that protects the fish from cold — giving the tomato plant similar frost resistance.
How Genes Help Build Proteins
Have you noticed that when a rabbit gets cold, the fur on its ears and paws turns darker? That’s because cold temperatures trigger the production of a specific protein that causes the fur to become black.
A gene controls the instructions for making this protein. Genes contain coded information for building proteins. Inside every cell, the DNA includes step-by-step instructions that cells use to make proteins.
Proteins play vital roles in all parts of the body — including the muscles, organs, and even the smallest cell structures. Without proteins, the body couldn’t build or function properly.
Important Concept: Genes Build Proteins
Genes contain the instructions for making proteins — the building blocks of life. Each gene carries a specific code that tells cells how to assemble the right proteins at the right time.
These proteins are essential for all functions in the body, from creating skin and muscles to carrying out chemical reactions. Without genes, cells wouldn’t know how to build the materials they need to survive.
Cells Divide
All living things begin life as a single cell. But how does one cell lead to billions of cells in a complex organism like a human?
Cells divide through a process called cell division, which occurs throughout life to enable growth and repair. In most cases, cells duplicate their contents before splitting, producing two identical cells. This is shown in Figure.
Sometimes, however, cells divide differently. In a process called meiosis, one cell divides to form four genetically different cells. This occurs during reproduction, as seen in Figure.
In mitosis, the chromosome number stays the same in each new cell. But in meiosis, the number of chromosomes is cut in half. Why might this be important for reproduction?
Common Mistake: Mixing Up Mitosis and Meiosis
A common mistake is thinking that all cell division results in identical cells. This is true for mitosis, which creates two identical cells used for growth and repair.
However, meiosis is different. It occurs during the formation of reproductive cells and produces four genetically different cells with half the number of chromosomes. Confusing the two processes can lead to misunderstanding how organisms grow and reproduce.
When Cell Division Becomes a Problem
Some of the cells in our body, like skin cells, constantly divide to replace older cells. Normally this process is balanced. But sometimes, due to a disruption in the cell cycle, cells divide too rapidly — which can lead to cancer.
Environmental factors can increase cancer risk. These include harmful substances like pesticides used in agriculture, or air pollution caused by burning fossil fuels.
Can you name any other environmental or lifestyle factors that can lead to cancer?
Did You Know?
Cigarettes and tobacco contain substances that increase the risk of cancers such as oral and lung cancer. This risk isn't limited to smokers alone — even people who breathe in secondhand smoke in polluted air are at risk.