Eli5: We have a dna correction system to avoid variations, but, sexual reproduction to promote variations. So, Are variations good?
In: Biology
Let’s take a look at two fairly extreme examples: Bananas and Sickle Cell Anemia. The first is an example of how lack of variation is bad, and the latter is an example of how variation is dangerous, but possibly beneficial.
The most common type of banana found in grocery stores is the Cavendish. All of the Cavendish banana trees are grown from cuttings, and the trees are basically clones, with identical DNA. This means that the fruit is very similar, but it also comes with a major risk. All the Cavendish banana trees are vulnerable to the same diseases, and are constantly at risk of being wiped out by fungus. This actually happened to the previous most common/popular banana variety, the Gros Michel. It is only with great effort and constant vigilance that bananas don’t get wiped out by fungus. That’s the danger of having no variation. If there’s a disease, or environmental change, that every member of a group is especially vulnerable to, then that group can get wiped out easily.
Now consider Sickle Cell Anemia. This is a genetic disorder that causes red blood cells to grow malformed, and not carry oxygen as well as they should, and break down easier. People who have it live shorter lives, even with medical treatment. However, people who carry the gene that causes it are also resistant to Malaria. So this is a genetic variation that is both a negative and a positive, depending on a number of variables. For people living in climates where Malaria is endemic, having one copy of this recessive gene gives them a better chance at surviving a serious disease, but they also have a chance to have children with two copies of the gene, giving them a debilitating disease (and also making them more vulnerable to Malaria.) For people living in other climates, the gene is always a negative, and few people descended from ethnic groups living in cold climates have it.
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