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Gene Flow: Definition & Examples

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  • 0:00 Definition of Gene Flow
  • 1:30 Examples of Gene Flow
  • 2:16 Gene Flow & Genetic Diversity
  • 4:35 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Chances are you've probably witnessed gene flow today! This lesson will define gene flow and give examples. It will also explain why gene flow creates genetic diversity.

Definition of Gene Flow

You're enjoying a sunny Saturday afternoon at the river. Suddenly the wind picks up, and a cloud of pollen blows in from the other side of the river covering you and the surrounding white spruce trees behind you. You might be thinking, 'Oh no, my allergies!' or 'My new white shirt is covered in yellow pollen!', but after this lesson you'll probably stand up and shout I just witnessed GENE FLOW! (Okay, maybe not but I can hope).

Gene flow is the movement of genes from one population to another population, more specifically, the movement of different alleles, or forms for genes (but we'll get to that later). In this case, the pollen (plant sperm) moved across the river from one population of white spruce to another. Genes are what is inherited from an organism's parents and what give the offspring certain characteristics, and alleles are different forms of a gene. For example, there are several different alleles for eye color genes, such as blue alleles (blue eyes) and brown alleles (brown eyes).

There is a little bit of debate in the science world about the definition of gene flow. Some believe that the movement of the actual genes (like you witnessed at the river) is gene flow, whereas others say gene flow is when the genes move into a new population and fertilization occurs, resulting in offspring (what you witnessed at the river + baby trees from the pollen). We'll use both definitions in this lesson.

Examples of Gene Flow

There are many examples of gene flow, but here are a few:

  • Europeans inhabit North America and mate with Native Americans (you can tell that the population of people living in America looks very different than it did in the 1400s)
  • Domesticated reindeer in western Alaska escape and mate with migrating caribou, adding the alleles for short legs and tame behavior
  • A blonde-haired, blue-eyed family from Sweden moves to India where the children grow up, marry Indians and produce offspring who now have the blonde-haired, blue-eyed alleles
  • Farmed salmon escape and mate with wild salmon
  • Bees carry pollen from one population of flowers to another population

Gene Flow and Genetic Diversity

Gene flow creates diversity within a gene pool, or the set of genes in a population. Let's use the Swedish family as an example to illustrate increased genetic diversity within a gene pool. The Swedish family carries alleles for blue eyes and blonde hair. When this family produced offspring with the Indian population, the Indian gene pool's genetic diversity increased because of the additional alleles from the Swedish family. Genetic diversity, or the amount of different alleles within a population, is important for the long-term survival of a species.

Let's use a real-life example to illustrate this concept. In the 1900s, the Florida panther's population declined significantly due to habitat loss and hunting. By the 1990s there were less than 30 panthers left in the wild, and with only 30 panthers, there was less genetic diversity. Why? With less panthers, there are fewer alleles in the population.

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