Question

1. Explain three reasons why a mutation in a single allele might be difficult to detect in a population.

2. Why is natural selection the most likely evolutionary mechanism to lead to adaptation? Can any other evolutionary mechanism lead to adaptation? Be sure to elaborate on your answers.

3. In a hypothetical population of 100 frogs there exists a gene with two alleles, D and d. 28 of the frogs are homozygous dominant (DD), and 22 are homozygous recessive (dd). What is the frequency of heterozygotes in the population? What are the allele frequencies? How would the allele frequencies be different in the next generation if no homozygous individuals were able to reproduce?

Answer 1

1) Reasons why the mutation in a single gene is difficult to detect :

• Single gene disorders are caused by DNA changes in one particular gene, and often have predictable inheritance patterns.
• Recessive diseases are more difficult to trace through family trees because carriers of a mutant allele do not show symptoms of the disease.
• A change taking place within a single gene and maps to one chromosomal locus (“point”), a gene mutation is sometimes called a point mutation.

2) Natural selection the most likely evolutionary mechanism to lead to adaptation:

Mechanism for evolution is natural selection, which occurs when populations of organisms are subjected to the
environment.The fittest creatures are more likely to survive and pass their genes to their offspring,producing a population that is better adapted to the environment.

• The essence of natural selection is this unequal reproduction. Individuals whose traits better enable them to adapt to their environment.
• Natural selection is the only mechanism known to cause the evolution of adaptations, so many biologists would simply define an adaptation as a characteristic that has evolved by natural selection.
• The word “adaptation” also refers to the process whereby the members of a population become better suited to some feature of their environment through change in a characteristic that affects their survival or reproduction.