The genotype of individual 3:
(a) could be either Cc or CC
(b) must be Cc
(c) must be CC
(d) could be either CC or cc.
9. If individual 10 marries a woman homozygous for normal colour vision, the chance that they will have a colour blind son is:
(a) 50%
(b) 25%
(c) 0%
(d) 100%.
10. The genotype of individual 11:
(a) could be either Cc or cc
(b) must be Cc
(c) must be C
(d) must be c.
11. A scientific study was carried out to test the effect of commercially produced pyrethrum on an insect population on an isolated island. Pyrethrum was sprayed at weekly intervals for six months. During this time the climatic conditions on the island remained constant. It is known that the insects have a short reproductive cycle and reproduce at a constant rate throughout the year.
The graph below shows the changes in the insect population during the study.
(MESSAGE ME FOR GRAPH)
(a) The following paragraph describes how natural selection can be used to account for these changes in the insect population. Choose from the following words and fill in the blanks to complete each sentence. Each word may be used more than once.
advantage, evolution, identical, offspring, pyrethrum, reproduce, resistant, survive.
Within any population of insects, all the individuals are not ___________________. Some individuals possess a mutation that makes them __________________ to pyrethrum. In an environment that does not contain pyrethrum the pyrethrum resistant insects have no survival __________________ over non-resistant insects.
When ________________ is introduced into the environment, the insects that are ______________ to pyrethrum will _______________, while the others will die. The surviving resistant insects can then _______________, passing on their resistance to their ______________. This process produced varieties of insects that are _______________ to insecticides and is an example of __________________ by natural selection.
(b) Sexually reproducing insect species have a better chance of surviving environmental change than do asexually reproducing insect species. Account for this statement.
12. Give one example for each of the following and indicate how each provides evidence for evolution.
(a) Palaeontology
(b) Comparative embryology
(c) Comparative anatomy
13. Many other scientists had tried to discover the laws governing inheritance but had obtained conflicting and inconsistent results.
(a) Outline the experiments carried out by Gregor Mendel on the inheritance of shape in peas. Describe the crosses he made and the results obtained at each stage.
(b) Describe two aspects of Mendel’s experimental technique that led to him obtaining results that could be accurately explained.
(c) Give one reason why the importance of Mendel’s work was not recognised until some time after it was published.
14. Define the following terms relating to the study of genetics.
(a) gene:
(b) allele:
(c) heterozygous:
(d) dominance:
(e) phenotype:
(f) co-dominance:
15. The inheritance of ginger and tortoiseshell coats is controlled by the sex-linked, dominant orange gene, A, carried on the X-chromosome. Inheritance of sex in cats is similar to humans.
The action of the A gene is to convert black pigment that would be produced by black genes to orange.
If only recessive a genes are present, the cat will be black.
