| What is an haploid? | A sex cell (gamete) that contains one set of chromosomes |
| Whats a zygote? | fertilised egg cell |
| Whats a diploid? | A cell with the full number of chromosomes e.g. zygote |
| What are the 2 causes of variation? | 1)Genetic causes - mother & father inherited genes
2)Environmental caues - climate, diet, accidents, culture and lifestyle e.g. if you eat too much you will become heavier |
| How can mutations happen continually? | if the phenotype is suited to a particular environment. |
| What is natural selection? | A process where organisms that are better adapted to an environment will survive and have more offspring. |
| Describe natural selection interms of the perpered moth? | 1)During the nineteenth century, pollution killed off some of the lichens and soot deposits caused the bark on trees to appear darker.
2)Light coloured moths were no longer camouflaged and were eaten by birds.
3)The dark moths had a better camouflage. |
| Describe selective breeding? | 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. |
| Give 3 common desires in plants and 3 in animals. | Plants:
1)disease resistance in food crops
2)wheat plants that produce lots of grain
3)large or unusual flowers
Animals:
1)animals that produce lots of milk or meat
2)chickens that lay large eggs
3)domestic dogs that have a gentle nature |
| Give benifits and risks of selective breed. | Benifits:
1)new varieties may be economically important, by producing more or better quality food
2)animals can be selected that cannot cause harm, for example cattle without horns
Risks:
1)reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive
2)rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms, eg a high percentage of Dalmatian dogs are deaf
3)can create physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly |
| Give 3 uses of genetic engineering? | Diabetes-treated by injecting insulin
GM crops-resistant to insect attack or are herbicide resistant
Golden rice- contains beta carotene which is needed by humans in order to make vitamin A - which is essential for good vision. |
| Describe the process of genetic engineering | 1)Enzymes isolate the required gene, gene inserted into a vector, usually a bacterial plasmid or a virus.
2)Vector inserts the gene into required cells.
3)The genes are transferred to animal, plant or microorganism cells, during early development. This allows them to develop with the desired characteristics. |
| Give 5 benifits and risks of genetic engineering. | Benefits:
1)Genetic modification is a faster and more efficient way of getting the same results as selective breeding.
2)Improve crop yields or crop quality
3)Introduce herbicide resistance, results in less herbicides being used, as weeds are quickly and selectively killed.
4)Insect and pest resistance can be developed and inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop.
5)Sterile insects could be created such as a mosquito. They would breed, which would lead to infertile offspring. This may help with spread of diseases, such as malaria, dengue fever and the Zika virus.
Risks:
1)Transfer of the selected gene into other species. What benefits one plant may harm another.
2)Some people believe it is not ethical to interfere with nature in this way.
3)GM crop seeds are often more expensive and so people in developing countries cannot afford them.
4)GM crops could be harmful toxins from the crops have been detected in some people’s blood.
5)GM crops could cause allergic reactions in people.
Pollen produced by the plants could be toxic and harm insects that transfer it between plants. |
| Give 2 common examples of cloning in plants? | Cuttings:
1)branch from the parent plant is cut off, its lower leaves are removed, and the stem is planted in damp compost.
2)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. 3)After a few weeks, new roots develop and a new plant grows.
micropropagation:
1)explants are grown in vitro using sterile agar jelly that contains plant hormones and nutrients so they are more expensive and difficult to do than taking cuttings. |
| Give 2 common examples of cloning in animals? | Embryo transplants:
1)Sperm taken from bull with desired characteristic (milk yield)
2)Zygotes develop into embryos then removed from uterus
3)Embryos split to form more calf
4)Identical embryos transplanted into mothers
Adult cell cloning:
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. |
