تدريب Shadowing: CONTEMPORARY TOPICS 2 UNIT 11 BIOLOGY DNA TESTING - تعلم التحدث بالإنجليزية مع YouTube
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Hello.
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Today I'd like us to concentrate on DNA.
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We'll focus on DNA testing and specifically on DNA testing of people.
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Before I explain how it's done, I want to review a bit from the reading.
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Now, you'll recall that cells comprise every part of our body.
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Our DNA is in every cell.
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DNA contains genetic information like eye color, hair color, height, and many other traits passed down from a mother and a father to their child.
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So, each of us has our own DNA, our own combination of genetic information from our parents.
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For example, a brother and a sister may end up with the same color of eyes and hair.
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However, other genetic information received from the parents will be different, which is why they look different.
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For example, maybe the brother is short, like the mother, and the sister is tall, like the father.
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Keep in mind that DNA is in every cell in the body
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and that all of these cells contain the same genetic information.
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Now, let's look at how DNA testing is used to identify people.
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Scientists create a DNA profile, also called a DNA fingerprint.
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To do this, they need DNA from the person.
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They take samples from different parts of the body, like hair, blood, skin, fingernails, and body fluids.
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Next, they extract the DNA from the cells in these samples.
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Then, they read the DNA with a computer.
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They use the data to create the DNA fingerprint.
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Statistically, it's very unlikely that any two people will have identical fingerprints.
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Now, let's ask, how is DNA testing used?
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Well, there are many ways.
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For example, to identify an unknown accident victim, or to find out who the father of a child is.
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Now, here's an interesting one.
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In 1999, scientists used DNA testing to prove that the son of the French king,
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Louis XVI and Marie Antoinette, in fact, died in prison.
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He didn't escape as some people had believed.
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DNA testing identified the son's body.
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People have been arguing about this for more than two centuries.
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Another use of DNA testing is by police to solve crimes.
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For example, say there's a murder.
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The police have a suspect they think did it.
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in the crime lab, scientists use DNA samples from the suspect and DNA samples from the evidence at the crime scene.
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Then, they design what's called probes.
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When the probes are put in with the DNA samples from the suspect and the DNA samples from the evidence,
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the probes show if the two sets of samples match.
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DNA identification is very effective, but not 100% foolproof.
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For example, suppose the only evidence at the crime scene is blood from the suspect.
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If there's a match between a sample of the crime scene blood and the suspect's blood, this will help the police.
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However, a single match from just blood, in this case, isn't very strong evidence.
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In contrast, let's say the crime lab has four samples from the crime scene and four samples from the suspect.
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Hair, blood, fingernails, and skin samples.
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They design four probes, one for each sample, and they get four matches.
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Bingo!
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The police can now feel more confident that they have the right suspect.
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Why?
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Remember, I said DNA is in every cell in our body, and each cell contains all of our unique genetic information.
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Now, let's turn to how DNA testing is used in the medical field.
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Here, let's consider how genetics is being used to diagnose diseases.
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With diseases, most DNA tests are given for one of two reasons.
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either to find out if someone has a certain disease or to see if the person is at risk for developing it.
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Researchers have found more than 6,000 genetic disorders.
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A genetic disorder means something isn't normal in the person's genes, a mutation.
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A change in one gene can cause a disease
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and a DNA test can and show
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if someone has a mutation in a gene that puts them at risk for the disease.
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Notice, I'm not saying that a change in one gene will cause a disease, only that the risk is higher.
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We're learning more and more every day about genetic diseases.
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For example, it now appears that the disease Alzheimer's, which damages memory in older people, is linked to our genes.
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So, we have to ask, what are the pros and cons of DNA testing in medicine.
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On the positive side, testing might save lives.
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If a doctor can diagnose a disease in its early stages, the patient can get treated earlier.
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Or, if a couple wants to have a baby,
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they can use DNA testing to find out beforehand if any risks for problems or diseases exist.
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On the negative side, there's the issue of fairness.
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What happens if DNA testing reveals that we have a genetic disorder that could cause a disease, and that information becomes known?
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This brings us to some concerns about privacy.
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A DNA profile contains a lot of personal information.
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So I'd like you to think about the following questions.
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One, who should own the DNA fingerprint once it's made?
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Two, who should have access to it?
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3. How should genetic information be used? And 4.
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Would you want people, especially people you don't know, to have access to your DNA fingerprint?
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These are some of the ethical questions we face about how to use the scientific knowledge we have.
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So, please give these questions some thought as you review the lecture.
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That's all for now.
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