Mutations & Genetic Variation (DP IB Biology)

Mutations & Genetic Variation

• Differences exist between organisms of the same species

  • These differences are known as variation

  • Examples of variation include:

    • Coat colour in mammals

    • Body length in fish

    • Flower colour in flowering plants

• Variation results from small differences in DNA base sequences between individual organisms within a population

• There are several sources of these differences in DNA base sequences:

  • Mutation

  • Meiosis

  • Random fertilisation during sexual reproduction

Mutations

• The original source of genetic variation is mutation

• Mutation results in the generation of new alleles which can influence evolution of a species

• Mutations that take place in the dividing cells of the sex organs lead to changes in the alleles of the gametes that are passed on to the next generation

  • A new allele may be advantageous, disadvantageous or have no apparent effect

  • An advantageous allele is more likely to be passed on to the next generation because it increases the chance that an organism will survive and reproduce

  • A disadvantageous mutation is more likely to die out because an organism with such a mutation is less likely to survive and reproduce

• Mutations in a species are, in the long term, essential for evolution by natural selection

• Note that a mutation taking place in a body, or somatic, cell will not be passed on to successive generations, and so will have no impact on natural selection

• Mutation is the only source of variation in asexually reproducing species

NOS: Commercial genetic tests can yield information about potential future health and disease risk. One possible impact is that, without expert interpretation, this information could be problematic

• There are two types of genetic testing available

  • Clinical or medical genetic testing

    • This is carried out through healthcare providers such as doctors, nurse practitioners, or genetic counselors

    • Healthcare providers determine which test is needed, order the test from a laboratory, collect the DNA sample, send the DNA sample to a laboratory for testing and analysis, and importantly they share the results with the patient and ensure understanding of the test results and the implications to the individual and their families

  • Commercial genetic testing provides genetic tests marketed directly to customers

    • The test kits can be bought online or in stores

    • Customers send the company a DNA sample and receive their results directly from the genetic company or lab

    • Commercial genetic testing provides people access to their genetic information without necessarily involving a healthcare provider 

    • This can pose some problems

      • Commercially available genetic tests are not scientifically validated and can give inaccurate results

      • Unexpected information that a customer receives about their health, family relationships, or ancestry may be stressful or upsetting

      • People may make important decisions about disease treatment based on inaccurate or misunderstood information from their test results

      • Individuals often are not provided with genetic counseling