Life Sciences, Part 1

Question 1: Give some examples of the practical applications of genetic engineering.

Answer 1: Diagnostic and medical applications include treating diabetes with insulin, producing human proteins, treating hemophilia, anemia, and blood clots, and manufacturing hepatitis B vaccine. Gene therapy has been used to replace defective alleles with normal alleles. For example, if a patient has a condition caused by an enzyme deficiency, replacing the defective allele enables the person to produce that enzyme. Medical forensic applications involving DNA analysis include using it to identify individuals and solve criminal cases. Agricultural applications include crop modification to develop types of wheat, cotton, and soybeans that resist weed controlling herbicides. Plants can be altered to make them grow bigger or vaccinated to make them resistant to plant viruses and insects.

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Question 2: Define natural selection, gradualism, and punctuated equilibrium.

Answer 2: Natural selection: This theory developed by Darwin states that traits that help give a species a survival advantage are passed on to subsequent generations. Members of a species that do not have the advantageous trait die before they reproduce. Darwin's four principles are: from generation to generation, there are various individuals within a species; genes determine variations; more individuals are born than survive to maturation; and specific genes enable an organism to better survive.Gradualism: This can be contrasted with punctuationism. It is an idea in evolutionary biology that states that evolution involves long time periods of no change (stasis) accompanied by relatively brief periods (hundreds of thousand of years) of rapid change. Punctuated equilibrium: This can be contrasted with gradualism. It is the idea that evolution proceeds at a steady pace and does not include sudden developments of new species or features from one generation to the next.

Question 3: Discuss the rate of evolution and how it is affected by the variability of a population.

Answer 3: The rate of evolution is affected by the variability of a population. Variability increases the likelihood of evolution. Variability in a population can be increased by mutations, immigration, sexual reproduction (as opposed to asexual reproduction), and size. Natural selection, emigration, and smaller populations can lead to decreased variability. Sexual selection affects evolution. If fewer genes are available, it will limit the number of genes passed on to subsequent generations. Some animal mating behaviors are not as successful as others. A male that does not attract a female because of a weak mating call or dull feathers, for example, will not pass on its genes. Mechanical isolation, which refers to sex organs that do not fit together very well, can also decrease successful mating.

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