Question Video: Understanding Genetic Variation Science

Video Transcript

Imagine there are two populations of the same species of plant. Population X has been produced by asexual reproduction and population Y by sexual reproduction. A new disease is introduced to the area. Which population is more at risk? Why? (A) Population X, because this population will have less genetic variation. Or (B) population Y, because this population will have more genetic variation.

Reproduction is the process by which organisms produce offspring. It can occur either sexually or asexually. You might be more familiar with the type of reproduction of population Y, sexual reproduction. This reproduction type usually involves gametes, like the human egg and sperm cell from two parents. During fertilization, the two gametes fuse to form a zygote, which can develop into a new organism.

You might note here that the question asks about a sexually reproducing plant species rather than sexual reproduction in humans. But that does not matter, as sexual reproduction in plants functions in a similar way to that in humans, with the difference that the male gametes are found in a pollen grain. The fusion of parental gametes means that the offspring of parents from population Y receive different versions of genes from their parents. This in turn leads to different combinations of characteristics of the parents. The offspring has therefore a unique combination of characteristics and is genetically different from their parents and their siblings. As every individual of population Y is genetically different from any other individual from that population, the population has a high level of genetic variation.

Asexual reproduction is a type of reproduction which only requires one parent to produce offspring. The offspring of this one parent is genetically identical to the parent and therefore have the exact same features as the parent has. We say that these organisms are clones and that they have very little genetic variation. In the question, we’re told that a new disease is introduced into both populations. The arriving disease is here represented as blue specks.

Let’s first consider what happens to population X that arose through asexual reproduction and therefore contains individuals that are genetically identical to each other. Let’s assume that one plant from population X has a set of genes that cannot tolerate the disease. Then, every single plant in population X will be badly affected, since they are all clones of one another. The low level of genetic variation puts this population at risk of being completely wiped out by this disease.

Now let’s take a look at population Y, which has been produced by sexual reproduction. Each individual plant in population Y has a different combination of genes. Some plants may still be badly affected and might die from this disease. But not all the plants in this population have the same combination of genes. Some plants might have genes that help them fight off the disease. Some might even have genes that make them completely resistant to the disease. This means that even if some plants in population Y die, the entire group of plants will not be wiped out. The remaining plants will then reproduce further, passing on their genes and ensuring that future generations will also withstand a similar disease. Through genetic variation, a species has a higher probability to adapt and survive through unfavorable conditions.

Let’s return to the question which asks which population is more at risk. With what we have learned we can now answer that the population at greater risk of the new disease is population X, because this population will have less genetic variation.