11.5 Calculating genetic biodiversity

Question 1

The importance of genetic biodiversity

Answer 1

• Species that contain greater genetic biodiversity are able to adapt to changes in their environment, and are hence less likely to become extinct.
• This is because there are likely to be some organisms within the population that carry an advantageous allele, enabling them to survive in the altered conditions.

Question 2

Factors that affect genetic biodiversity

Answer 2

• Mutations in the DNA of an organism, creating a new allele
• Interbreeding between different populations. When an individual migrates from one population and breeds with a member of another population, alleles are transferred between the two populations. This is gene flow
• Selective breeding where only a few individuals within a population are selected for their advantageous characteristics and bred.
• Captive breeding programmes in zoos and conservation centres where only a small amount of captive individuals of a species are available for breeding.
• Often the wild population is endangered or extinct
• Rare breeds where selective breeding has been used historically to produce a breed of domestic animal or plant with characteristics which then become less popular so the numbers rapidly fall.
• Artificial cloning for example using cutting to clone a farmed plant
• natural selection: species will evolve to contain primarily the alleles which code for advantageous characteristics.
• Genetic bottlenecks: where few individuals within a population survive an event or change , thus reducing gene pool
• the founder effect: where a small number of individuals create a new colony, geographically isolated from the original.
• Genetic drift: due to the random nature of alleles being passed on from parents to their offspring, they frequency of occurrence of an allele will vary

Question 3

Measuring genetic biodiversity

Answer 3

• One way of measuring genetic biodiversity is by measuring polymorphism. Polymorphic genes have more than one allele.
• Different alleles exist for the immunoglobulin gene, which plays a role in determining human blood type - it is therefore defined as a polymorphic gene.
• The three alleles are:
  1) Ia - resulting in the production of antigen A
  2) Ib - resulting in the production of antigen B
  3) Io - resulting in the production in neither antigen
• Most genes are not polymorphic
• These genes are said to be monomorphic - a single allele exists for this gene, ensuring that the basic structure of individuals within a species remains consistent.
• The proportion of genes that are polymorphic can be measured using the formula:
  Proportion of polymorphic gene loci = number of polymorphic gene loci/ total number of loci
• The loci of a gene refers to the position of the gene on a chromosome