Edexcel Biology Gcse - Changing the Genes Part 3

The simplest way to clone a plant involves taking a cutting. This is an old but simple technique, used by gardeners. A branch from the parent plant is cut off, its lower leaves are removed, and the stem is 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 to keep it moist and warm. After a few weeks, new roots develop and a new plant grows.

Another way of cloning plants is by tissue culture. It works with small pieces of plants, called explants. These are grown in vitro using sterile agar jelly that contains plant hormones and nutrients. This makes tissue culture more expensive and difficult to do than taking cuttings. This is an important way to preserve rare plant species or grow commercially in larger nurseries.

1) Tissue sample scraped from parent plant

2) Tissue sample placed in agar growth medium containing nutrients and auxins

3) Samples develop into tiny plantlets

4) Plantlets planted into compost

1) Sperm is taken from a bull from a high yield dairy herd

2) Cow is artificially inseminated with sperm

3) Zygotes develop into embryos in cow and then removed from the uterus

4) Embryos are split into several smaller cells before they become specialised, each of which can grow into a new calf

5) Identical embryos are transplanted into host mothers

Embryo transplants

1) the nucleus is removed from an unfertilised egg cell

2) the nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell

3) an electric shock stimulates the egg cell to divide to form an embryo

4) these embryo cells contain the same genetic information as the adult skin cell

5) when the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

Diabetes is a disorder in which the body's blood glucose levels remain too high because glucose is not effectively removed from the blood. It can be treated by injecting insulin. The injected insulin acts just as natural insulin and causes glucose to be taken up by the liver and other tissues, which results in cells receiving the glucose they need, and blood glucose levels stay normal.

Bacterial cells have been genetically modified to produce substances such as human insulin.

Current genetically modified crops include those that are resistant to insect attack or are herbicide resistant, this produces increased yields. Herbicide resistant crops allow them to tolerate herbicide, but the weeds are killed by it, therefore less herbicide is needed.

Scientists have added a gene to wild rice that makes it produce beta carotene. This changes the colour of the wild rice to a golden colour. Beta carotene is needed by humans in order to make vitamin A which is essential for good vision.

The advantage of golden rice is that it can be used in areas where vitamin A deficiency is common, so it can help prevent blindness. In many countries golden rice is not being grown commercially over fears associated with genetically modified crops.

There are ethical issues involved in genetic modification, as well as concerns about the possible health risks of genetically modified food. For example, a genetically modified food might contain a substance that causes an allergic reaction in some people, or higher levels of a toxin naturally found in the food. Others think it is ethically wrong to create new life forms, or to move genes between different species.

In the future, researchers are hoping to use genetic engineering to be able to overcome some inherited disorders, such as cystic fibrosis and Huntington's disease amongst others.

1) Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are a short section of unpaired bases

2) A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.

3) The vector and the isolated gene are joined together by ligase enzyme.

4) The vector inserts the gene into required cells.

5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.

Genetic engineering is a faster and more efficient way of getting the same results as selective breeding.

Improve crop yields or crop quality, which is important in developing countries. This may help reduce hunger around the world.

Introduce herbicide resistance, which results in less herbicides being used, as weeds are quickly and selectively killed.

Insect resistance from Bacillus thuringiensis can be inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop.

Sterile insects could be created, such as mosquitoes. They would breed with fertile mosquitos, but be unable to reproduce. This would reduce the number of offspring and may help with spread of diseases, such as malaria, dengue fever and the Zika virus.

Transfer of the selected gene into other species. What benefits one plant may harm another.

Some people believe it is not ethical to interfere with nature in this way. Also, genetically engineered crop seeds are often more expensive and so people in developing countries cannot afford them.

Genetically engineered crops could be harmful, for example toxins from the crops have been detected in some people's blood.

Genetically engineered crops could cause allergic reactions in people.

Pollen produced by the plants could be toxic and harm insects that transfer it between plants.

1) Decide which characteristics are important enough to select.

2) Choose parents that show these characteristics from a mixed population. They are bred together.

3) Choose the best offspring with the desired characteristics to produce the next generation.

4) Repeat the process continuously over many generations, until all offspring show the desired characteristics.

1) Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are short strands of unpaired bases.

2) A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.

3) The vector and the isolated gene are joined together by ligase enzyme.

4) The vector inserts the gene into required cells.

5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.

Action: Remove competing plants from the crop growing area

Treatment: Herbicide spray

Explanation: Allows more energy to be transferred to the crop

Side effect: Reduces biodiversity. May have harmful effect on health.

Action: Remove animals that feed on the crop

Treatment: Pesticide spray

Explanation: Prevents energy being transferred from the crop to consumers

Side effect: Reduces biodiversity. May poison helpful organisms.

Action: Keep animals indoors

Treatment: 'Battery' farming

Explanation: Reduces energy transferred to environment so more energy available for growth

Side effect: Increased risk of disease. Lower quality product. Ethical concerns.

Biological control is an alternative to using pesticides. By releasing a natural predator into the crop growing area, the number of pests can be reduced. This can have unforeseen consequences as the numbers of different organisms in the food web are changed. There have been examples of the predator becoming a more serious pest than the original problem.

Men are more likely to be colour-blind because it is a sex-linked disorder.

There are over three billion base pairs in the human genome.

Restriction enzymes are used to cut DNA in genetic modification.