Consider a population of 150 mice on an island, with allele frequencies B = 0.20 for brown coat colour, and b = 0.80 for white coat colour. Brown (B) is dominant to white (b) and the population is in Hardy-Weinberg equilibrium. Twenty-five homozygous brown mice from the mainland float to the island on an uprooted tree after a storm. What are the genotype frequencies before migration? What are the allele frequencies after migration? Now, suppose the twenty-five brown mice float away again on another tree without breeding, and the island is back to its original state. Allele frequencies on the island are back to B = 0.20, b = 0.80. On the continent, there is a large population of many thousands of mice, with allele frequencies B = 0.80, b = 0.20. One year, human ships begin moving back and forth between the island and the continent, and occasionally a mouse comes along for the ride, and stays and breeds. Equal numbers of mice ride in each direction. The shipping trade continues indefinitely. Where will the allele frequencies ultimately stabilize and why? (Assume that no other forces are affecting allele frequencies.)
Gene Flow
Gene flow, also known as gene migration, is the introduction of genetic material from a particular population to another population of the same species through interbreeding. For example, a bee facilitates its reproductive process by carrying pollen from one flower to another. The flow alters the composition of the gene pool of the receiving population. It introduces new alleles within the population and helps increase variability. This exchange of genetic material occurs through reproduction and brings about new combinations of traits into the population. Where human beings are concerned, actual migration of populations, whether voluntary or forced, brings about gene flow.
Population Biology
Population biology is the study of patterns in organism populations, specifically the growth and management of population size, population genetics, the evolution of life history, species interactions, and demography.
Speciation
The process of speciation involves the formation of new species during evolution. The new species evolve in such a way that both new and old species are not able to interbreed. Thus, speciation occurs when few members of one species get separated from the main species due to geographical, mechanical, or reproductive isolation. These separated members develop new traits that make them different from the main species. In other words, speciation could be defined as the absence of gene flow between two populations that become new species.
Allele Fixation
A gene is a unit of heredity and contains both physical and functional information that shapes an individual. Genes are made up of DNA (deoxyribonucleic acid), which carry genetic information from one generation to another, from one set of parents to their offspring, and so on. Every cell in a human body, or any living organism, has the same DNA, which implies that every cell in an individual’s body has all the information it needs to build and sustain the body!
Consider a population of 150 mice on an island, with allele frequencies B = 0.20 for brown coat colour, and b = 0.80 for white coat colour. Brown (B) is dominant to white (b) and the population is in Hardy-Weinberg equilibrium. Twenty-five homozygous brown mice from the mainland float to the island on an uprooted tree after a storm.
- What are the genotype frequencies before migration?
- What are the allele frequencies after migration?
- Now, suppose the twenty-five brown mice float away again on another tree without breeding, and the island is back to its original state. Allele frequencies on the island are back to B = 0.20, b = 0.80. On the continent, there is a large population of many thousands of mice, with allele frequencies B = 0.80, b = 0.20. One year, human ships begin moving back and forth between the island and the continent, and occasionally a mouse comes along for the ride, and stays and breeds. Equal numbers of mice ride in each direction. The shipping trade continues indefinitely. Where will the allele frequencies ultimately stabilize and why? (Assume that no other forces are affecting allele frequencies.)
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