| CONTENT | NOTES | LEARNING ACTIVITIES |
| 3 Mutation. | | |
i Characteristics of mutant alleles, to include random occurrence and low frequency. | When dealing with mutant alleles, candidates should be able to interpret data on gene mutation frequency.
| Analyse information on sickle cell anaemia. View and discuss information obtained from computer simulation. |
ii Mutagenic agents.
| Mutation rate can be increased artificially by chemical agents or irradiation. | |
iii Changes in the number of chromosomes through nondisjunction. | | Examine photographs of human karyotypes including Down’s Syndrome. |
iv Polyploidy: advantages in crop production.
| In dealing with polyploidy, the terms triploid and tetraploid need not be known. It will be sufficient for candidates to know that polyploidy is a condition in which an individual possesses one or more sets of chromosomes in excess of the normal diploid number. In crop plants this often confers increased vigour. | |
v Change in the structure of one chromosome (duplication, translocation, deletion, inversion). | | Obtain and interpret information relating to mutation from the examination of appropriate material, for example normal/spelt wheat, popcorn/podcorn cobs, normal/albino mice. |
vi Alteration of base type or sequence (substitution, insertion, deletion, inversion). | The effect of gene mutations on amino acid sequences should be noted. | |
b) Selection and speciation | | |
1 Natural selection. | | |
i The survival of those organisms best suited to their environment.
| In the evolution of new species, the effects of isolating mechanisms, mutations and selection on the gene pool should be covered. | |
| ii The concept of the species. | | Examine data on species of animals and flowering plants endemic to Scotland. |
iii The importance of isolating mechanisms as barriers to gene exchange leading to evolution of new species. | | Examine maps to show the distribution of organisms between different continents. |
| iv Adaptive radiation. | | Obtain and present information on the distribution of British buttercup species. |
v The high-speed evolution of organisms such as antibiotic resistant bacteria and the melanic peppered moth.
| | Obtain and present information on heavy metal resistance in grasses, calcicole/calcifuge pairs in Viola species or the bladder campions. Analyse and interpret current data on distribution of peppered moths. |
vi The conservation of species through wildlife reserves, captive breeding and cell banks. The maintenance of genetic diversity. | | |
2 Artificial selection. | | |
i The evolution of a wide variety of crops and domesticated animals through selective breeding and hybridisation as undertaken by humans. | | Examine information on artificial selection in, eg Brassica oleracea, cattle, dogs. Analyse information on selective breeding by means of suitable computer simulation. |
ii The contribution of genetic engineering to the development of new varieties.
| In genetic engineering, the importance of being able to locate genes or groups of genes on chromosomes must be known. This can be done by gene probes or by the recognition of characteristic banding patterns. Once located, endonuclease enzymes are used to cut DNA fragments and ligase enzymes are used to seal new genes into the genome of other organisms such as bacteria. Examples to include the manufacture of insulin and human growth hormone. | |
iii Somatic fusion in plants to produce new species.
| Somatic fusion is used to overcome sexual incompatibility between plant species. The technique involves the removal of the cell walls by the action of cellulase enzyme so that protoplasts can be fused. | Prepare and examine plant protoplasts.
|
All