General Ethical Dilemmas

Many of the general ethical dilemmas which arise in relation to genetic testing are not exclusive to this technology. As with all new developments in medicine, it is an ethical requirement that genetic tests are of proven safety and efficacy and that the benefits outweigh the risks and burdens before they are introduced into routine clinical practice. The stage at which technology moves from research to clinical application is as much an issue for genetic testing as it is for new treatments for cancer or heart disease. Those who believe that humanity exists as part of a divine plan may object to genetic testing on the basis that it seeks to interfere with natural processes or is a further manifestation of human hubris. Doctors are frequently accused of playing God'. If this were to mean that humankind should refrain from decision making about life or death, almost every kind of medical intervention would be precluded. We, however, be able.to draw boundaries which separate inter-. vent ions which are justified from those which are not. People who do not accept an absolutist religious position may nevertheless be unhappy about the attempts of humans to take ever greater control over their lives and the lives of their off spring. While we must accept that society has probably now lost the concept of children being born 'as nature intended', the continual striving for new developments in medical technology and ways of prolonging and improving life can sometimes manifest itself in what seems to some an almost obsessiveness for immortality or control. From another perspective, however, it has been suggested that increased genetic self awareness 'will help bring about the more rational attitude towards the inevitability of death of which modern societies (and healthcare systems) are in great need'.

Level of support for the child

There are concerns that as prenatal diagnosis becomes more widespread, those who decide not to have testing when they are known to be at risk of a genetic disorder, or who decide to continue with an affected pregnancy, may come to be seen as irresponsible. Where the child will be severe ti disabled and require long term and expensive treatment it is possible that society will become increasingly unwilling to pay for the necessary care, seeing the parents as 'to blame' for the birth and therefore individually responsible for the cost of treatment. In the USA there have been reports of private insurance companies attempting, unsuccessfully, to withhold reimbursement for medical care of children whose disability was detected before birth." With the increasing use of private medical insurance in the UK it is possible that a similar path may be trodden in this country. Any such moves must be vigorously opposed. The availability of resources for the care and treatment of a disabled child must not be contingent on whether the parents knew of the disability before the child was born.

Media perceptions

The media  naturally preoccupied with how genetic advances will affect people's lives in a dramatic manner.By concentrating on issues like genetic engineering or Cloning, they:seldom. mention how advances. in genetic technology may offer affected by genetic problems the only hope of attaining a reasonable standard of health or a normal lifespan.It transportation to allow the extreme or exceptional aspects of medicine's potential to dominate current debate in a way that obscures emote immediate goals of genetic technology.Whilst recognizing the poet.initial, for misuse,should,not lose sight of low.practice within genetic services focuses, on mitigating the tragic ace. of genetically transmitter.13etter ways of managing genetic conditions are, in the MBA's view, the main purpose And rationale of this technology.

The Wedge

The wedge is a kind of inclined plane. The difference is that an inclined plane stays in one place, but a wedge moves. One common use of a wedge is for splitting logs to make firewood. Wedges are sometimes used under doors to prevent them from blowing shut. The Egyptians may have used wedges to split the rocks that were used in building the pyramids. By hammering several wedges into a crack between two layers of rock, the rock could be weakened. Eventually the rock would split. 

The Screw

The screw is similar to the inclined plane and the wedge. It is an inclined plane that is rolled up. You can see this if you cut a right-angle triangle of paper, darken the long side, and roll it around a pencil as shown in the drawing. The pattern that results is much like the thread on a screw. If the inclined plane has a gentle slope, the thread will be fine. If the slope is steep, the thread will be coarse. You can follow the edge of the paper around the pencil with your finger and see how it makes a spiral. Screws are used to join pieces of wood or metal. When you use a wood screw, you apply a turning force to the screwdriver with your hand and wrist. As the screw turns, the threads pull the screw into the wood. In other words, a screw changes a turning force into a pulling force. Threads have many uses. The lids of jars and pop bottles are often threaded so that they can be closed tightly. Bolts and nuts depend on threads for doing their task of holding things together.

The Pulley

The pulley is a wheel that turns around an axle. A groove in the edge of the wheel allows a rope to pass over it or under it without slipping off. There are two kinds of pulleys fixed pulleys and movable pulleys. In a fixed pulley, the wheel turns but the arm holding the wheel is fixed in one place. A movable pulley moves up or down while the wheel turns. 

Sometimes the two kinds of pulleys are combined. The drawing at the left on the next page shows one fixed pulley and one movable pulley, used together to lift a load. The load is easier to lift this way than with a single fixed pulley. In fact, you can overcome a resistance of 50 N in this way with an effort of only 25 N. A block and tackle uses two fixed pulleys and two movable pulleys. With this combination, you can overcome a resistance of 100 N with an effort of 25 N.

The Wheel and Axle

 A wheel and axle machine is just that a wheel fixed to an axle, like the steering wheel of a car. When a steering wheel is turned, the axle, or shaft, turns with it. It would be impossible to turn the steering axle by grasping it in your hands. The wheel that is attached to the top of the axle makes steering possible. By grasping the rim of the wheel, the driver can easily apply enough force to turn the axle. The doorknob is another common example of the wheel and axle machine. As with the pulley and the lever, the advantage of greater force is matched by a disadvantage of increased distance.

The Lever

The lever may have been the first machine man learned to use. Cavemen almost certainly knew how to move a heavy rock with the help of a strong pole. All they had to do was to force one end of the pole under the rock and put a smaller rock on the ground under the pole near the same end. By pushing down on the other end of the pole, they could raise the rock. 

About 4000 years ago, the Great Pyramid was built in Egypt. It took about 30 years to build. There is no record of how it was built, but the lever may have been the principal machine used. Great teams of workmen may have levered the massive blocks of limestone out of quarries (workweek), dragged them to the site of construction, and then used inclined planes built of sand to raise them up onto the pyramid. Each block has a mass of about. Today, levers are more popular than ever. They are used in many household tools, such as scissors, pliers, the crowbar, and the claw hammer. 

Simple Machines

There are just six kinds of simple machines. Each kind has many uses. Big machines are merely many simple machines put together. The six kinds of simple machines are the lever, the pulley, the wheel and axle, the inclined plane, the wedge, and the screw.

The Meaning of Work

In everyday conversation, we use the word work in various ways. "Going to work", "doing homework", "a writer's work" these are some common expressions using the word. The meaning of "work" varies. But, to the scientist, "work" has the same meaning every time it is used. In science, we say that "work" has been done only if a force of some kind has moved an object from one place to another place. "Work is done when a force moves an object through a distance" is how scientists describe it. 

You are doing work, in the scientific sense, if you lift a bag of potatoes onto your shoulders. You use a force to raise the bag through the distance from the floor to your shoulders. Once the bag is on your shoulders, no more work is being done because there is no motion. The amount of work you did depends on the amount of force you had to use and the distance through which you moved the potatoes. For example, you do work whenever you stretch a spring or an elastic band. The more you stretch it, the more work you do.

Machines 

The modern world is filled with machines. Some of them are very simple, such as the can opener, the shovel, and the saw Others are more complicated, such as the bicycle, the lawn-mower, and the crane. All machines are designed to make work easier. There are three ways in which they can do this by increasing the force, by increasing the speed, and by changing the direction of the force. Here is an example of each of the three ways.

Musular Force

Muscles make it possible for animals to move. They are attached to the bones. Most muscles are controlled by the brain. Messages from the brain travel through nerves and tell the muscles when to act. Unused muscles go soft. Exercise and a proper diet that includes lean meat, milk, and cheese help to build strong muscles. 

The force Of Friction 

When two surfaces are rubbed against one another, one tends to stick to the other. Friction is the force that causes this. No surface is perfectly smooth. Even the smoothest looking surface, when examined with a microscope, will be seen to have bumps and hollows. These bumps and hollows resist one another when two surfaces are rubbed together. The force of resistance is called friction. Friction can be useful. Rub the palms of your hands together, pressing hard. Do this quickly several times. Your hands begin to feel warm. This shows that friction produces heat.

What Can Forces Do?

Forces can make things move. They can also act on stationary objects without causing motion. Sometimes we use a force on an object that is already moving, to stop it. A train uses a braking force as it approaches a station. Similarly, when astronauts were about to land on the moon, rockets were used to slow down their craft, so it could make a soft landing. Forces can also change the direction of motion. This happens in baseball when a batter hits the ball. The ball is first slowed down, then stopped for an instant, then shot off in a different direction. 

 The Force Of Gravity

This is the force that pulls objects down to the ground. when we say a rock is heavy, we mean that the force of gravity pulling down on it is a strong force. To lift the rock off the ground, you must use a force that is slightly greater than the pull of gravity. Once the rock is moving upwards, the lifting force becomes equal to the gravity force. The force of the Earth's gravity is what holds the moon in its nearly circular path around the Earth and prevents it from flying off into outer space. Similarly, it is the force of the sun's gravity that keeps the Earth and the other planets in their orbits.

Culture Media

A culture medium must contain a balanced mixture of the required nutrients, at concentrations sufficient to allow a good growth rate. If a nutrient is in excess, it can inhibit growth or even be toxic. Often one nutrient is present in limiting quantities, to allow adequate growth while preventing the microorganisms from multiplying at their maximum rate. By moderately slowing down the growth rate, the microorganisms are kept healthy. Usually a mineral base is made, containing all the possible nutrients in inorganic form. To this can be added a carbon source, energy source, nitrogen source and growth factors, to suit the organism being cultured. A medium composed entirely of chemically defined nutrients is called a synthetic medium. A medium which contains some ingredients of unknown chemical composition, such as malt extract, is called a complex medium.