body chromosomes clones cytoplasm genes nucleus sex Information is passed from parents to their young in... cells.

Transcription

1 Genetic variation and its control 1. The diagram shows a human cell and some of its contents. (a) Choose words from this list to label the diagrams. chromosome cytoplasm gene nucleus Choose words from this list to complete the sentence. a body cell an egg cell a gamete a sperm cell In the cell above, the chromosomes are found in pairs so this cell must be... (3) (Total 4 marks) 2. These young rabbits look like their parents. This is because information about characteristics such as fur colour is passed from parents to their young. Choose words from this list to complete the sentences below. body chromosomes clones cytoplasm genes nucleus sex Information is passed from parents to their young in... cells. Each characteristic, e.g. fur colour, is controlled by.... The structures which carry information for a large number of characteristics are called.... The part of the cell which contains these structures is called the.... Page 1 of 8

2 (Total 4 marks) Page 2 of 8

3 3. A market gardener produces large numbers of attractive, large flowered geranium plants. (a) Give two advantages to the gardener of producing geraniums from cuttings rather than from seeds Gardeners often cover trays of cuttings with large polythene bags. Suggest one advantage of this. (Total 3 marks) Page 3 of 8

4 4. The diagram shows one method of producing herbicide-resistant crop plants. Root tissue cultured Mature plant (herbicidesusceptible) Herbicide-resistant gene transferred into cells Tissue split into individual cells Cells multiply Cells form embryos Embryo grows into a plant Mature plant (herbicideresistant) Page 4 of 8

5 (a) (i) The herbicide-resistance gene is obtained from a herbicide-resistant plant. Which structure in a cell carries the genes? (ii) How is the herbicide-resistance gene cut out of this structure? (c) (d) Apart from having the herbicide-resistance gene, the herbicide-resistant plants are identical to the herbicide-susceptible plants. Explain why. Suggest one advantage to a farmer of growing herbicide-resistant crops. Many people are opposed to the growing of herbicide-resistant crops produced in this way. Suggest one reason why. 5. Tetra is the first monkey to be cloned. The method is described below. A sperm and an egg were combined and the resulting embryo was allowed to split into two cells, then four, then eight cells. At the eight-cell stage, the embryo itself was split by scientists to produce four two-cell embryos. The four embryos were then implanted into surrogate mothers. Three of the embryos did not survive. The fourth, Tetra, was born 157 days later. Her name means one of four. (Total 6 marks) Page 5 of 8

6 (a) Explain why this method could produce several identical monkeys. Suggest two reasons why these monkeys would be valuable in trials of new treatments for human diseases (Total 4 marks) 6. Read the passage about IVF (in-vitro fertilisation) and embryo-splitting. IVF is not as successful as we would like it, says scientist Michael Tucker. On average, only one in five or one in six of all the embryos that we generate in the IVF lab will develop as far as full-term delivery as a baby. There is a way to perhaps double those odds. A new, identical embryo is split off from the original embryo made in the IVF lab. What we are really doing is creating an identical twin, says scientist Dr Hilton Kort. And that s what happens in nature every day. Cloning is creating a replica of a person or an animal. (a) Explain why the two embryos will develop into identical twins. Explain why the embryos are not clones of their parents. Page 6 of 8

7 (c) The scientists want to develop this technique, but are afraid to do so because public opinion might be against the technique. Suggest an explanation for this. 7. Read the following passage. (Total 5 marks) The first cloned-to-order pet sold in the United States is named Little Nicky, a 9 week old kitten delivered to a Texas woman saddened by the loss of a cat she owned for 17 years. The kitten cost its owners $ and was created from DNA from her beloved cat, named Nicky, who died last year. He is identical. His personality is the same, the owner, Julie, told The Associated Press in a telephone interview. She asked that her last name and home town not be disclosed, because she said she fears being targeted by groups opposed to cloning. The diagram shows how Nicky was cloned. (a) Explain, as fully as you can, why Little Nicky is identical with Nicky. (3) Page 7 of 8

8 Julie fears being targeted by groups who disagree with cloning. (i) Suggest one group of people who might disagree with the cloning of pet cats. (ii) Explain why the group might disagree. (Total 5 marks) 8. Many insecticides contain active ingredients called pyrethrins. These are extracted from pyrethrum daisies. These plants are grown in Kenya, a developing country in Africa. They provide income for farmers and valuable exports. An American biotechnology company has now transferred the gene for making a specific pyrethrin to brewers yeast. This can be grown easily, so this pyrethrin can be produced cheaply. However, insect populations can build up resistance to specific pyrethrins. (a) What are the advantages and disadvantages of using brewers yeast to produce pyrethrins? Describe, as fully as you can, how a gene for making pyrethrins is transferred from daisy to yeast. (6) (3) (Total 9 marks) Page 8 of 8