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Animal cloning

People may want to clone a plant deliberately. Cloning of plants has many important commercial implications. It allows a successful variety of a plant to be produced commercially and cheaply on a massive scale in a short space of time.

Cuttings

The simplest way to clone a plant involves taking a cutting. A branch from the parent plant is cut off, its lower leaves removed and the stem planted in damp compost. Plant hormones are often used to encourage new roots to develop. The cutting is usually covered in a clear plastic bag at this stage to keep it moist and warm. After a few weeks, new roots develop and a new plant is produced. The method is easy enough for most gardeners to do successfully.

Tissue Culture

Another way of cloning plants is by tissue culture, which works not with cuttings but with tiny pieces from the parent plant. Sterile agar jelly with plant hormones and lots of nutrients is needed. This makes tissue culture more expensive and difficult to do than taking cuttings.

Organisms have sex cells called gametes. In human beings, the male sex cells are called sperm and the female sex cells are called eggs or ova.

In human beings, each gamete contains 23 chromosomes, half the number found in the other cells of the body. When the male and female gamete fuse, the new embryo contains the full 46 chromosomes – half from the father and half from the mother.

Tissue culture involves the following steps:

Small amounts of parent tissue or a number of cells are taken

The plant material is transferred to plates containing sterile nutrient agar jelly

Plant hormones are added to stimulate the cells to divide

Cells grow rapidly into small masses of tissue

More growth hormones are added to stimulate the growth of roots and stems

The tiny plantlets are transferred into potting trays where they develop into plants

Embryo Transplants

A developing embryo is removed from a pregnant animal at an early stage, before the embryo’s cells have had time to become specialised. The cells are separated, grown for a while in a laboratory and then transplanted into host mothers.When the offspring are born, they are identical to each other and genetically related to the original pregnant animal. They are not related to their host mothers because they contain different genetic information.

Fusion Cell Cloning

Fusion cell cloning involves replacing the nucleus of an unfertilised egg with the nucleus from a different cell. The replacement nucleus can come from an embryo, but if it comes from an adult cell, it is called adult cell cloning.

'Dolly the sheep' was the first mammal to be cloned using adult cell cloning. She was born in the UK in 1996 and died in 2003. Here’s how she was produced:

An egg cell was removed from the ovary of an adult female sheep, and its nucleus removed.

The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell.

The fused cell then began to develop normally, using genetic information from the donated DNA.

Before the dividing cells became specialised, the embryo was implanted into the uterus of a foster mother sheep. The result was Dolly, genetically identical to the donor sheep.

Genetic Engineering

Genetic engineering is also called genetic modification or GM. It is not the same as cloning. Although cloning techniques are used in genetic engineering, the two things should not be confused.

Certain enzymes can cut pieces of DNA from one organism, and join them into a gap in the DNA of another organism. This means that the new organism with the inserted genes has the genetic information for one or more new characteristics. For example, the organism might produce a useful substance, or be able to carry out a new function. We say that the organism has been genetically modified.

The animation shows how the method can be used to produce bacteria that produce insulin. This is a human hormone and valuable to people with diabetes. Bacteria reproduce quickly, so a lot of insulin can be made quickly.

Enzymes- proteins which catalyse or speed up chemical reactions inside our bodies.

DNA- the material inside the nucleus of cells carrying genetic information. DNA stands for Deoxyribonucleic acid.

Bacteria- single celled micro-organisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium.

Hormone- chemical messengers produced in glands and carried by the blood to specific organs in the body.

Diabetes- a serious disease in which the body is unable to regulate blood sugar.

There are strong arguments for and against cloning and genetic engineering. It is possible to produce genetically modified animals and plants. Sheep that produce human proteins for treating the symptoms of cystic fibrosis - a disease which causes sufferers to produce abnormally thick and sticky mucus in their lungs - have been produced, and even tobacco plants that glow in the dark when they need watering.

Some people are excited by the almost limitless possibilities of cloning and genetic engineering, while some people believe the process is unethical and should be banned. Others are concerned about what might happen in the future.

Blood Pressure

Arteries carry blood away from the heart. The blood in the arteries is under pressure because of the contractions of the heart muscles. This allows the blood to reach all parts of the body.

Blood pressure is measured in millimetres of mercury, mmHg. There are two measurements:

systolic pressure - the higher measurement when the heart beats, pushing blood through the arteries, and

diastolic pressure - the lower measurement when the heart rests between beats

A young, fit person may have a blood pressure of about 120 over 70, which means their systolic pressure is 120 mmHg, and their diastolic pressure 70 mmHg.

Blood pressure varies with age. It also varies with lifestyle factors such as:

diet

stress

exercise

body mass

alcohol consumption

Aerobic respiration Aerobic respiration requires oxygen. It happens in cells when glucose reacts with oxygen. Here are the word and symbol - higher only - equations:

glucose + oxygen → carbon dioxide + water (+ energy)

C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)

Energy is shown in brackets in each equation because it is not a chemical substance.

Anaerobic respiration Anaerobic respiration does not need oxygen. It happens when there is not enough oxygen for aerobic respiration. Here is the word equation:

glucose → lactic acid (+ energy)

Much less energy is released by anaerobic respiration than by aerobic respiration.

During hard exercise when anaerobic respiration occurs with aerobic respiration, an oxygen debt builds up. This is because glucose is not broken down completely to form carbon dioxide and water. Some of it is broken down to form lactic acid. Panting after exercise provides oxygen to break down lactic acid. The increased heart rate also allows lactic acid to be carried away by the blood to the liver, where it is broken down.

Extremes of blood pressure can create problems. High blood pressure can cause:

kidney damage

burst blood vessels

damage to the brain, including strokes

Low blood pressure can cause:

fainting

dizziness

poor blood circulation

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