Номер C, страница 158 - гдз по английскому языку 11 класс учебник Комарова, Ларионова

Learn about science. Units 11 and 12 - номер C, страница 158.

Условие.

C Now read the text and decide whether your answers were correct.

The unique finger

Forensic scientists can identify criminals and their victims in many different ways now, but the fingerprint is still the most effective means of identification. A fingerprint is unique. Each individual has a slightly different pattern on the tips of the fingers, and even if the skin is removed, when it grows back the same pattern reforms. There are tiny sweat glands in the fingertips and when we touch different surfaces, an imprint is left behind.

Fingerprints are not always visible to the naked eye, but at a crime scene, police have a number of methods for finding prints and inputting them into computer systems. Most commonly, a black powder such as ninhydrin is brushed over an area. The powder sticks to the oil from the fingerprints and the print becomes visible. The prints can then be photographed or collected using tape. If a print is on a substance like paper which is porous, the police can use iodine to make the print show up, then, photograph it. Prints will also show up under the light from an an argon laser.

Surfaces can be dusted with fluorescent powder for this to work. Police rarely uncover a complete fingerprint, yet computer systems can find a match to even a small part of a print. Ninety-two per cent of fingerprint matches in the US are completed using the computer system with no human intervention.

Now researchers are looking at ways to lift fingerprints from cloth. They are trying to use a metal vapour which rests on top of the fingerprints. This doesn't yet allow police to make a fingerprint match, but it would be a way to discover whether or not a person has really been the victim of an attack.

My DNA or your DNA

DNA fingerprinting is relatively new. Examples of our DNA can be found everywhere because it is in our cells. So, there is DNA in our hair, in our saliva, on our skin and in our blood. The chemicals in DNA are always the same, but everybody's DNA is linked up in a slightly different pattern so our DNA, or genetic make-up, is more or less unique.

DNA fingerprinting is a way to identify criminals, but it is difficult. To analyze DNA, you need to get the DNA out of the hair, skin, saliva or blood sample. This is a complex chemical procedure

and errors are always possible. However, if a DNA pattern is identified successfully, it is a very effective method of finding dangerous criminals. As with fingerprints, there are databases of the DNA profiles of dangerous criminals and the police can use these systems to find a match.

Usually, however, to identify the criminal, police will need to match two DNA samples. The police may need special permission to take a DNA sample from a suspect.

Other clues

There are other ways to identify criminals or victims. There are other unique patterns in the human body and without realizing, we carry clues which show what we have been doing or where we have been.

A soil sample carried on the soles of our shoes can be evidence of having been present at the scene of a crime. A victim can be identified using dental records, or a criminal could be found using the imprint of lips on the side of a glass. If a crime has been committed, it is likely that something will point the police in the right direction.

Even though not scientifically proven, body language can tell us whether or not a suspect is lying. When lying, people tend not to look you in the eye, they are not as relaxed and their body movements are more strained.

Science may make crimes easier to solve, but it doesn't mean there are less of them.

Решение.