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.This is bad for a population because if there are any changes in the environment, such as disease, all members are similar and what kills one panther, will kill all panthers. The remaining Florida panthers had a plethora of health problems, including: parasites, heart defects, and males had poor sperm quality.
In an attempt to save the panthers, eight female pumas, which are a sub-species of the Florida panther, were brought to Florida from Texas.Gene flow from the eight pumas increased the genetic diversity of the Florida panthers. Although the Florida panther is still an endangered species, it has not gone extinct, and the population has tripled. The population is still at risk, but the increased genetic diversity from the pumas has increased their chances of survival.A study from the U.S. Department of Agriculture, the University of Maryland, and North Carolina State University looked at genetic diversity and survival rates in honeybees.
They found that the more mates a honeybee queen has (increased gene flow), the more alleles are present in her gene pool (increased genetic diversity), the greater chance the colony of bees would survive. Females who mated with less than seven males had a 17% chance of survival after 10 months versus a 48% survival rate for those who mated with seven or more.
As you dust off the pollen, you’re probably excited to know that gene flow occurred between the two tree populations, and the trees behind you can now experience greater genetic diversity. Here are some important terms to take with you when you leave the river:
- Gene flow is the movement of genes from one population to another population. Examples of this include a bee carrying pollen from one flower population to another, or a caribou from one herd mating with members of another herd.
- Genes are what you inherit from your parents and they give you many of the characteristics you possess.
Genes can come in different forms called alleles.
- You can see examples of gene flow everywhere you go, from the bees transferring pollen from one population of flowers to another to the Swedish-Indian family living across the street.
- A gene pool is the set of genes in a population.
- Genetic diversity is the amount of different alleles within a population and is important for the long-term survival of a species (Florida panthers and honeybees). Like gene flow, you can see genetic diversity everywhere; just look at your friends, chances are they have different skin tones, hair colors, and eye colors.