Images of mutants and mutations often conjure up thoughts of dramatic monsters created from laboratory accidents. Mutants resembling slime green fluorescing creatures resulting from the unintended fusion of containers of radioactive goo might be the quintessential depiction in our imaginations.
These images mostly stem from the stereotypes depicted in the movies, books, and societal influences we have absorbed. In truth, mutations seldom exhibit such extreme changes. Additionally, mutations are not inherently harmful; in truth, some can be quite advantageous.
Exploring Beneficial Genetic Mutations
Let's begin by examining DNA to understand the concept of beneficial mutations at a genetic level. DNA is made up of a phosphate backbone connected to nucleosides like adenosine, thymine, guanine, and cytosine. These nucleosides bond with each other through hydrogen bonds, allowing them to intertwine and aid in creating the distinctive DNA double-helix coil.
A mutation happens when a DNA segment with a specified nucleotide sequence undergoes a modification in one or more nucleotides. For example, if a gene is supposed to contain a thymine (T) nucleotide at position 7, but an error in DNA replication (frequently induced by DNA polymerase) causes a cytosine (C) nucleotide to be incorrectly inserted instead, this forms a mutation.
Another nucleotide can be substituted for one, as shown in the previous instance, referred to as a point mutation because the change happens at a single point.
Sometimes multiple nucleotides in sequence are altered from the original, intended strand; and this collection of alterations can be termed a mutation as well.
Determining if a mutation is beneficial based only on its sequence is not possible. A beneficial mutation provides positive traits, such as improved fitness, to the organism possessing it. While less frequent in nature, beneficial mutations often spread more rapidly through the population compared to random mutations, possibly due to natural selection.
Exploring Beneficial Mutations in Humans
Having gained an understanding of the genetic implications of beneficial mutations, let's delve further and explore some advantageous mutations present in our world. Our focus will be on beneficial mutations found in humans. Noteworthy examples encompass:
- Lactose tolerance:
- Did you know that lactose tolerance, the ability to digest lactose found in milk, is actually a mutation? Most humans are born lactose tolerant, but as we age, many of us lose this ability and become lactose intolerant. However, some populations have a higher natural tolerance to lactose due to their historical access to large amounts of milk from animals like cows, goats, and sheep.
- In ancient times, milk was a valuable source of calories, nutrients, and vitamins for our ancestors. Those who could digest milk were more likely to survive and reproduce, passing on their gene for lactose tolerance. This genetic mutation is a simple point mutation, where a cytosine nucleotide is replaced with a thymine nucleotide.
- Abnormally high bone density:
- A rare mutation known as "LRP5" has been discovered, which results in abnormally high bone density. This mutation prevents the typical activity of a receptor involved in osteoporosis, making individuals with this mutation resistant to bone injuries and degeneration, even from serious accidents or aging. Scientists are studying this mutation to potentially help those with weaker bones.
- Resistance to insulin resistance:
- Doctors have identified a gene called SLC30A8 that confers resistance to insulin resistance (diabetes) in some individuals. Those with this mutation are over 50% less likely to develop diabetes under the same risk factors as those without the mutation.
More Beneficial Mutations Examples
- Disease: Malaria
- Mutation: Hemoglobin C mutation
- Population: In certain populations of Sub-Saharan Africa, the hemoglobin C mutation provides resistance to malaria, reducing susceptibility to the disease.
- Disease: HIV
- Mutation: CCR5 (an HIV receptor)
- Population: Some people of North European descent have a modified CCR5 gene that makes them totally immune to HIV.
- Disease: Heart disease
- Mutation: Apolipoprotein A-I Milano
- Population: In certain Italian townships, a mutated Apolipoprotein A-I gene leads to more efficient cholesterol clearance, reducing the risk of cardiovascular disease.
Beneficial Mutations in Animals and Microorganisms
- Animal: Cows
- Mutation: Murray Gray coloring and increased fitness.
- Effects: Cows with this mutation exhibit greater fertility and higher progeny numbers.
- Organism: Bacteria
- Mutation: Antibiotic resistance.
- Effects: Bacteria develop resistance to antibiotics through mutations, enabling them to survive medication applications.
- Animal: Fish
- Mutation: Antifreeze proteins (AFP).
- Effects: Fish in cold climates have mutations in antifreeze genes, enhancing their survival in Arctic waters.
List of Features of Beneficial Mutations
1. Beneficial mutations do not arise more frequently solely due to their advantageous nature. Mutations happen randomly, with the majority being harmful (deleterious) or neutral (having no effect), rather than beneficial.
2. Beneficial mutations, like all mutations, may result from either a single nucleotide change (point mutation) or modifications affecting larger segments of DNA.
3. Beneficial mutations are defined by their ability to increase survival, reproductive capacity, and/or competitive advantage.
4. Beneficial mutations spread more rapidly in a population compared to random mutations because of natural selection.